IPhone blocking calls!!

for about the last 3 weeks, my iPhone will no longer allow me to receive texts or calls from number that are not in my contacts. It doesn’t ring, then it indicates I have a voicemail from an unknown number, and won’t let me access that either, unless I add the number to my contacts? I’ve googled and looked through my settings and there is nothing obvious. I used to be able to receive all calls and choose to block individual numbers but I can’t do that anymore. I’ve missed 3 really important calls as they weren’t in my contacts and it’s driving me mad!!! Any ideas welcome, thank you 🙃