What about the APN settings? I didn't read where you did that.
Also, a few phones don't work on some networks. For that you have to call up your new carrier.
Finally, service may be poor to non-existent where you are. Try it at their shop or sales counter.
I unlocked my phone (Optus Locke’s Alcatel pixi4-4)and put another providers sim in and sent a text but it did not arrive for a while so I googled how to tell if it was unlocked and so I followed their instruction ;settings>networks >more>mobile networks> then say said to click on the network provider tab and it came up with if you search for new network connections you will be disconected from your current network at the time I didn’t know what that meant I was just following there instructions but now I think that was where I went wrong. No sooner had I clicked that did the text that I sent earlier get received and so I stopped what I was doing and a few days later when I put my sim in it says network connection error and since I have not been able to use.
Any help much appreciated. Thanks