Not hell bent on anything , if you called the appropriate BT number 08000851756 , (presumably the correct number if it were on the BT email ) , then it’s unclear why the cancellation wasn’t straight forward, and the cancellation not put in place immediately.
Both the OTS and NOTS system before it don’t require anything other than the new ISP to start the ball rolling , the consumer doesn’t need to contact the old provider themselves, that’s the entire point from the regulator point of view , if the customer has decided to switch they don’t want the old provider having the option to dissuade the consumer from switching…this obviously opens the system to mistakes as in your case , misidentifying your address for the customer that called address, and abuse , like slamming or even malicious actors looking to cause disruption.
I’ve never defended what’s happened , I queried if the correct process to cancel was followed , as often a customer doesn’t follow the instructions to cancel the migration correctly , but if you did follow the correct procedure to cancel the change , and that wasn’t actioned that’s an error on BT ‘s part .
…but to the main point , why is it that easy for a ISP to start migrating a customer without consent, that’s because Ofcom want it like that , their view is the ease to switch , having to only contact a new provider, outweighs the problem of slamming or misidentification of a customer address, before OTS and NOTS , the process was you called your old provider, asked for a MAC ( migration authorisation code ) , you gave this to the new ISP , this system had inbuilt checks ( a call to both the old and new provider was necessary being the main one ) Ofcom got rid of that .
