Signal problem iPhone 11

[#1]

Purchased 2nd hand iPhone 11, confirmed unlocked and not stolen. Transferred plusnet sim from iPhone 8 and no signal on iPhone 11. Maybe the occasional bar when travelling. But still no service, got replacement sim and same story. Tried giffgaff and Vodafone sims and they worked. Sent back to shop and they said no problems, Tried their sims and they worked. Any suggestions?

[#2]

Hi there,

Try going to Settings > General > Profile then deleting anything there. 

Sometimes a profile of another provider can interfere with our service.

Let me know if that works! 

[#3]

Hi, not able to do that on iPhone. Have read other phones are able to fix the problem by adding apn but can’t do that either on iPhone.

[#4]

Not a problem, will it allow you to change what is there to the ones shown here? 

They may be the same but I would need you to edit what's there and type them in again, if it will let you.