Was your number always a BT number , or has there been any number portability on it , moving it between different network providers , often when consumers get incoming calls from some sources but no incoming calls from others , it’s down to the portability process not being done correctly …If it’s always been a BT number and the issue only occurred when you moved to DV ( assuming you are on DV and your phones plug into the router ) , then it may be something to do with that , but it’s less likely as you probably wouldn’t get any incoming calls at all if the BT PSTN to DV change was messed up.
FYI , interrupted dialtone is an alert to tell you the line is on divert , obviously if calls to a number that is set for immediate divert to elsewhere, the phone on divert won’t ring ( but that wouldn’t explain calls from mobiles getting through) , modulated dialtone ( so two tone dialtone rather than on-off , on-off dialtone ) let’s you know a message has been left on the answer service
