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Three Sim 4G Issue
Quick question/observation regarding a new 3 Prepay20 sim. A friend asked me to see if I could get a contract free sim card broadband solution for her where she would have unlimited data. I suggested the 3 Prepay20 but I've had issues setting it up.

LTE/4G works perfectly when the sim is in an android phone but as soon as I use it on a LTE router it refuses to connect. I did manage to get 3g working for a while with very slow speeds but as soon as I switched to LTE the connection dropped again. Can't even get 3g connectivity now. This was using a Huawei B593. I also tried the SIM in a Microtik SXT exterior router with no connectivity whatsoever. The router gets a signal but just no data.

I though it may be an APN issue but the phone APN ("internet" Seems to be an O2 sim) will not work with either of the LTE routers. I've also tried all the 3 APNs. I've used 48 sims with no issues whatsoever in both of these routers with excellent results.

I'm just wondering if anyone has had similar issues or are Three doing something now to prevent new phone sims from working in LTE routers (i.e. non android/ios devices).

Any thoughts/contributions well appreciated!
That indeed is a concern as Three prepay used to be one of the easiest to set up, i.e. you could buy an unlocked router, put the SIM in and it would connect without doing anything in the web interface. Basically Three's SIMs would connect no matter what was typed in the APN settings.

I haven't encountered a new Three SIM that uses the former O2 configuration other than on business Three bill pay, so I just have a few suggestions:

Check the antenna settings on the B593 router. For example, if you were using it with an antenna with 48 and now are testing it with Three without any antennas attached, it will have trouble transmitting as it would be trying to use the antenna ports.

With the MikroTik, it needs "Use network apn" to be set to no (steps here). It also mentions how to clear a stuck IP address, which I've had an issue with when switching SIM cards.

Enable data roaming on the router. I remember some O2 broadband SIMs requiring this to be enabled to connect after merging with Three.

Try the former O2 broadband APN: open.internet

Try pinging to see if there is any connectivity. If this pings out fine, you can try changing your PC DNS settings to and as a test.

Try the SIM one more time in a phone just to make there is not a Three related outage in the area since trying it in your routers.
Hi Seán, thanks you so much for the detailed reply. Last night was spent doing a lot of testing with various routers to try and find the root of the issue. First to dispel any fears of using a new Three Prepay20, it does still work but with some caveats. From my testing the issue seems to be that the sim will connect on the 3g network only if the router doesn't have a roaming option that can be enabled. The sim had no issues connecting using an android phone.

I have 3 routers that were used for testing; the Huawei B593s-12 (Speedport II), the Mikrotik SXT-LTE and the Mikrotik LHG-LTE (the dish type). Firstly, all three router worked easily and hassle free with a 48 sim card. All that was needed was to enter the sim pin number and the 48 APN, so I was sure that my routers didn't have issues. On testing the new 3 sim card, the only router that I could get 4g on was the LHG-LTE, the other two failed with the B593s only picking up 3g. When the B593 was switched to LTE mode the red roaming icons appeared on the top right and it couldn't connect. There are no options to enable roaming on the B593. (is using the original Telecom firmware). I've tried all the various 3 APNs and had the same result with each one.

Huawei B593s-12 : Connects on 3g, no connection on LTE (possible due to roaming settings)
Mikrotik SXT-LTE : No connection whatsoever even when the 3g band was selected
Mikrotik LHG-LTE : Full LTE connection without issues

Again, all three worked flawlessly with a 48 sim.

I hope this information will be of help to someone else. I'll have a chance to test another new Three Prepay sim over the weekend so it'll be interesting to see if I have the same results. I'll post my findings on Monday.

If you don't mind me asking, what would be the most cost efficient LTE router the use instead of the B593? Thanks a mill!
That looks like the roaming issue I recall seeing with former O2 SIMs. I wonder why the SXT-LTE model wouldn't work as this router should have roaming support. You can try the following from its command line:

Enable roaming:
/interface lte set lte1 allow-roaming=yes

Force it to use the Three network code (27205 = Three, 27202 = former O2):
/interface lte set lte1 operator=27205

Set back to automatic network selection:
/interface lte set lte1 operator=""

The cheapest two routers I'm aware of are the Huawei B311 (£63 at time of posting) and the TP-Link TL-MR6400 (£75 at time of posting). Both are LTE Category 4, i.e. no carrier aggregation support. Those 3 routers above are also LTE Category 4.

The Huawei B311 only has one SMA antenna port, so would be less suitable if the indoor reception is weak. The TP-Link MR6400 has two external antenna ports - The rabbit ear antennas attaches to its SMA ports.

The Huawei B535 (£120 at time of posting) is LTE Category 6 capable (supports 4G+ carrier aggregation), supports the new 700MHz band (4G band 28) and has two SMA antenna ports.
Just a quick update Seán, I've tried the changes you suggested and after a but of unresponsiveness from the webfig and a few resets and reboots it's now working perfectly on the SXT. Next task is to figure out how to view those settings rather than changing them (I'm new to RouterOS) and I'll be happy out!

Thanks for the budget router suggestions! I may try an Eir or Gomo sim on the B523 first and see how it goes, it would save the necessity of shelling out for the better routers (my friend is on a tight budget right now unfortunately!).
That's great, best to not touch the SXT config in the meantime until you back it up. Smile

To create a backup, enter the following command:
/system backup save

You can use Winbox to download the backup or to later upload it there after a reset. This MikroTik Wiki goes into more detail on how to manage and restore backups.

To view the current LTE settings, go into Interfaces -> LTE -> lte1 in Winbox or type this command:
/interface lte print

To view the APN profile, go into Interfaces -> LTE -> lte1, touch the wrench icon, then select select LTE APNs or type this command:
/interface lte apn print

An Eir prepay SIM should work in the router and would be a good option to try before signing up to a GoMo bill pay plan. From my experience, GoMo and Eir work with either the APN or Both have a 120GB monthly usage allowance, after which it is throttled to around 5Mbps for the remainder of the month. As GoMo works natively on the Eir network (same MNC of 27203), it does not require roaming to be enabled, so should work in that B593s-12 Speedport II.
Thanks a million for all the information Seán, it was extremely helpful. Fount the exact same issues with the second new Three sim, connection to 3G worked fine but in order to access LTE it needed to be enabled on the both the Mikrotik LHG and SXT routers. I'll have an Eir sim in a few days so that should take care of the B593s-12 issue.

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