Sim Card Errors

I’ve been having this issue for awhile and I’ve tried customer service before, but no luck.  It has now spanned multiple phones.(I have a BYOP sim)  I don’t have access to services that used to work.  If I try to turn on things like call waiting, or use call forwarding I get “Network or SIM card error”.  The last time I tried to contact customer service, they said there was an issue with a prior call forwarding request pending and they would clear it and set the call forwarding for me.  They did.  It worked.  Then I went to my settings to turn the forwarding off.  It gave me the same error.  The CS rep had to turn it back off.  Call forwarding would be very useful to me for work and I can’t set it myself.  The call waiting not working is also frustrating.  Has anyone else had issues with this that they were able to resolve?