Thank you for your post and welcome to our community forums. We're here to help.
I am really sorry to hear that you're having some issues with making phone calls at the moment. Are you having problems with any other mobile service? For example, any problems receiving calls, making or receiving texts, using mobile data, etc.?
If you can confirm of any other service issues you're having, this can help us to narrow down what's going on and to see if a replacement SIM card would help to alleviate things.