Its possible that your final issue wasn’t actually anything to do with number portability, there is a relatively common fault on PSTN ( System Y exchanges ) , where someone calling a number hears ‘ringtone’ in the earpiece of the instrument making the call , but the landline phone at the address being called doesn’t ‘ring’ if the handset were pickup up the call would connect, its caused by an equipment fault in the exchange not sending out ringing current to actually make the called phone ‘ring’.
If there were thought the issues were with number portability , that could cause the wrong things to be looked at , ( misdiagnosis ) the fact an engineer managed to get it sorted suggests they may have moved your line from a faulty System Y line card onto an OK one, fixing the problem .
This issue doesn’t affect DV lines , it’s one of the reasons why DV is necessary, as the exchanges are pretty old now and liable to issues like this , ‘bell not ringing’ is the fault ‘code’ , being a throwback to when telephones actually had a bell inside them .
