No service (GSM signal: 3G/4G and SMS but wifi works fine)

Hi !

I hope you’re all doing good :)

I recently changed the screen and the battery of my Iphone 6. Everything was working just fine for a week until yesterday. I can neither receiver / send SMS, nor access 3G/4G.

J'ai démonté et remonté l'écran et la batterie

• I disassembled and reassembled the screen, the battery and the coax connexion
• I restored the phone and the carrier parameters
• The IMEI is still running
• The SIM card works on other phones
• I downloaded the last IOS and Itunes version

What should I do ?

Could it be a motherboard issue or a welding issue ?

Would it be worth trying to replace the lightening dock ?

Thanks in advance for your help !

Margaux