All phone calls are silent on both ends

[SS3]

Every phone call I make or receive is completely silent on both ends. Not distortion or static, just silence - I can't hear them and they can't hear me. This is the case when calling different people, when calling from different locations, when using speakers, etc. It's only for phone calls and not for WhatsApp, FaceTime, or any other form of audio call. All other audio from my phone is working normally, as are texts. My balance is topped up. I've had this issue for several weeks and Apple says it's a problem with the Sim card, according to a diagnostics test. I have an iPhone XS Max.

This is becoming extremely inconvenient since the only medical appointments I've been able to get are phone appointments and I've already missed one because the doctor couldn't hear me and I couldn't hear him. A fast resolution would be very helpful.

[MI5]

They all work still.

Live chat is subject to availability and you cal call using Skype over wifi which should work as WhatsApp calls are.

Guide: A Guide to Skype 

[SS3]

I can't find live chat and Skype isn't letting me call because they apparently don't have Skype for the 0800 number as the post you linked recommends. The only options are to invite them or to pay, and I really don't want to have to pay for the privilege of contacting my provider for help when the service I pay them for stops working.

[MI5 · Accepted solution]

@SS3 

Lots of 0800 numbers to try here but many others have called using Skype without issues.

Guide: Coronavirus Community Help and Support 

[SS3]

Ah thank you, a different 0800 number worked. Took a while but they're sending me a replacement that should hopefully arrive in time. Thanks for all your help MI5

[MI5]

You're welcome @SS3