When ppl call me goes to vm

For 4 weeks now when someone calls me it goes to voicemail after one ring. Now when someone calls me it says to call a different # ( some random # ) & when you do it says that voicemail box is full.

Have:
Swapped SIM card
Replaced my apple device
Spoken to apple for 3 hours
Spoken to Tech service from Telus who say it’s an apple problem. ( it is not )