Although BT as your provider are responsible for delivering your service ( incoming and outgoing) you have to accept that number porting isn’t within the control of any one company ….you say you have had the phone number for 38 years so presumably you were a ‘BT’ customer when you first got that number…but at some point to obviously exported it to another provider ( at least one , the last being Sky ) ….are you still at the same address you were at when you were last a BT customer with this number ?
When you make an outgoing call and your ‘correct’ number is displayed on the phone of the person you have called , then BT have provisioned your line with the correct number , and you would probably find that other BT customers can call your landline…the issue will be with incoming calls from other networks , like Sky themselves, and other networks like TalkTalk , and mobile phone network operators.
At the moment ( for example ) a Sky customer calls you, Skys network should in effect interrogate the number they dialled , and conclude it’s a ‘BT customer’ number , and send the call off to BT, when your number was ported to Sky , the same call on the Sky network would conclude that the number ( all though a BT number ) was now part of the Sky network and internally route the call to you , through Skys own equipment ( Sky customer to Sky customer )
I suspect, at the moment the call intended from a Sky customer to you , is still being internally routed through Sky , and as you are no longer connected to Sky , the call never arrives…the same can happen with some other non BT providers , if they continue to think your number is still associated with Sky , these networks send the call off to Sky network, where it gets internally routed ,instead of Sky sending it off to BT , but you are not on Sky network anymore , so the call disappears into Sky network and never connects to you.
It seems relatively commonplace for this type of thing to happen , and ( in your case ) Sky have no incentive to do much if anything in the way of resolving this, after all you are no longer a customer of theirs, however as BT are your provider , they should do what they can, but ultimately they cannot access Skys network equipment and enter the required changes themselves.
What other networks have you noticed this with , if these people that cannot get through are non BT customers then this will probably be the reason why the calls to you fail.
Another approach would be for the people who call you , but cannot get through , is to report the issue to their own network provider , so ( for example ) a current Sky customer says to them , ‘I cannot get through to this number 01***, ******, I know they are in , but they say the line doesn’t ring’ , chances are in the first place they will say ‘the fault must be with that number and not us’ , if they persist, Sky may take a closer look…obviously this can be done at the same time you have your BT fault report open
