The letter P next to contacts in my recents list.

My wife’s iPhone 15 pro has a letter “ P “ next to the contacts in her recents list.

When she calls out, no-one can hear her talk, so when she calls me, I just say I’ll call you back and she hangs up, and I call her back and it’s all good then, so at first she can receive, but not transmit.

We have the latest updates.

Question is, how do I get 1 sim active and not 2. How do I get rid of the primary or personal “P” next to her contacts. I have the same phone, but have any issues.

Any help would be much appreciated