Hi StevieGoodman92,
Welcome to the community and thanks for posting. I deeply apologise for the troubles you've been experiencing with incoming calls. I can see how much of an inconvenience this is.
This sounds to me like it could be signal related as a replacement SIM hasn't made any difference.. Could you please answer the following questions:-
What is the make and model of handset you're using?
Do notice this happening more when you're at home?
If so, put your postcode into the EE Network Status Checker. Does it show an issue?
If you go outside of your area, can you then receive calls fine?
Look forward to your reply.
Thanks