I cannot receive incoming calls on my iPhone 13. “User busy “

Everyone that tried calling my phone today says they keep getting my voicemails, or I’m receiving random voicemails with no missed calls or a call even being made. Until at one point I noticed a call actually calling but the top banner popped up for a second, not long enough to try to answer then cancels the call it’s self and on the banner under who’s call me it says “user busy”? Like I’m the busy user. Never seen it before . I have tried everything. Apple or xfinity could help it’s been hours of stress . I’ve reset all my settings and network settings 3 times each and nothing at all. I seen someone else with this issue, is she saying to just back up her data and things on phone and do just a general favor reset ? That fixed it ? I never posted or used anything here before so I am sorry however this chooses to send or land . I just hope someone can help. Thank you in advance .