A quick Google reveals 2 models of that watch, @danbutterworth - perhaps this will help?
Check the steps below:
Samsung watch setup.
1. Contact O2 and get them to set up Data and WIFI calling on your Samsung mobile, it's free but needs to be set up to use the watch, no clue why. You can then turn the switch on in setting under connections.
2. If you need an esim the only place to get it now is at an O2 store, don't waste your time calling 202 or going on O2 chat, they won't supply, it's free at the store.
3. If you already have an esim you won't be able to set up your watch just by going through the process on the Gear app, it'll set up the plan in principle on the phone and watch, but it won't connect to the network so don't waste your time and drive yourself mad. Delete the plan and go to an O2 store.
4. The only way you'll get the watch connected is by going to the O2 store, sitting with the sales person and have them set up the esim and the plan, it's £5 per month for 1gb which is more than enough data.
5. Most store sales people haven't a clue about setting up the Samsung watch 4g, so have them give you the esim, scan the QR code let your phone set up the plan and then have them go into their system as if your purchasing the watch directly from O2, at the bottom of their screen (this is at an O2 store) there is a box that says set up watch plan, when they press that, it'll allow them to set up a watch data plan, as if you've purchased the watch from O2, very poor set up as their O2 techs have no clue about what they are selling.
6. At that point and after the salesperson puts in all the info from the esim they gave you into their system, it'll take about 10 min for the watch to connect, you'll then need to go into the connection settings on your watch, turn on auto for data, turn on data roaming and then go to the network search setting on the watch and let it the watch search for the network, it'll then register it and you're almost there.
7. Next go to your mobile and in settings, advanced, turn on the switch to use your mobile data on other devices, make sure when you turn it on, it shows your Samsung watch at the bottom, tap and another screen comes up showing the watch is connected to your phone.
8. Then reboot your watch and your mobile and your done. Test it by leaving your phone in your home and take a walk, the watch should connect and show the 4g symbol and the mobile calling bars, if you try and make a call and it doesn't work or says connect to Bluetooth, go back to step 7, and reboot the phone to make sure it's found the device, i.e. your watch. It will also say at the bottom of the watch, standalone, means your using the watch on it's own.
9. You're done. Just remember you can only get your Samsung Watch 4g connected by getting it done in the O2 store.
I haven't played with SmartWatches, so took a stab... 🤷♂️
That's generally what customer services do too
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