No audio or mic sound on normal calls but data e.g. fb/wa calls work

I recently repaired an iphone 11, full housing swap

Everything worked perfectly for months then we noticed that there was an issue with normal calls after a few months

When using Whatsapp/Facebook the microphone, earpiece and speaker work perfectly

However, when we use normal calls we can't hear the other person (on either speaker/earpiece) and they can't hear us

Things I've tried:

• New sim
• New digital sim
• Wifi calling
• Upgrade iOS
• Factory reset
• Different apple IDs
• Tried checking app permissions
• All usual sound settings

Just to note signal etc is fine

I know for a fact the hardware works, I just can't get it to work on normal calls - I'm assuming there must be something that tells them to activate on call thats sent bad?