iPhone 12. Can’t call out or text

[Smollet]

I had an issue with my email address as I couldn’t send out or receive. Contacted BT who provides my broadband band access and they helped me to reset my password. However I can now no longer receive or make texts or calls. As a result I can’t contact them or O2 who are my phone line provider. I’ve also lost my BT landline.
Any thoughts