Can't set up cellular on apple watch
I recently bought an apple watch series 5 (GPS + Cellular). I got a new line for my watch added to my account and should be able to set up cellular, but I've been unsuccessful. Every time I try to set up cellular via the watch app on my phone, I get the error message "SVC_EMSI_BE_ERROR". I've called 611 numerous times and unpaired the watch as told, but nothing works. It's been very frustrating. Any advice?
Watch: Series 5 with GPS + cellular
Phone: iPhone 6S running on iOS 13.6 (should be compatible with series 5
The watch works fine within the range of my phone, of course.