IPhone 13 not receiving landline calls or texts from non-iPhone sources

My iPhone 13 has suddenly stopped receiving any communication, whether calls or text messages, from landlines and non iPhone mobiles. If I call my iPhone from my home landline I get a dead line, even though I can call my landline no problem. If I try to use a website which requires an automated text service (e.g. approving bank card payments) I do not receive the text. If however I send a text using Message to another phone, it’s fine, and I can receive messages and calls from iPhones no problem. I have reset my phone, reset network settings, turned the phone off and on, checked Do Not Disturb, everything which is usually suggested. My carrier (O2 in the UK) can’t see anything wrong.