Call issue.... (phone number alway busy ‭on this device)

I can no longer get incoming calls on my phone without miscellaneously being interacted. I previously thought it was the a fault from the telecom service provider. Upon their checks- they said my number is okay & has no issue & hence, I try in on a different phone 📱 which I did any all calls were ‘coming in as usual’... With this device, of late, anyone who call’s me gets ‘number busy’ as a feedback as if I have blocked all contacts on the phone - However, I come to see notifications of these calls as ‘missed calls’ ...... It’s becoming frustrating as I like phone but it’s underproductive @iOs. Please! help.

Details of the effected iPhone S.E

Software Version: 14.3DX3W281ZHTVV

Modele Number: MP852KN/A

Serial Number: DX***TVV

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