The chances are you did have a phone line , if you chose to not plug a phone into the master socket , or if on DV ( Digital Voice ) the router , that’s up to you , but the facility is there to make and receive calls, you can get broadband without any telephone service , but this doesn’t have a phone number so it’s impossible to raise call charges , you cannot have had that type of broadband service.
If you enquired with another provider , even if you subsequently cancelled any order you made with that other company before they actually took over service , the result is exactly the same as if the order was never raised in the first place , so it’s odd that these calls took place in that (upto ) 2 week period, given that this period is absolutely no different to before , or after you cancelled the other ISP.
The question is then , what makes this 2 week’s ‘special’ ?, if nothing physically has changed yet , it suggests you didn’t actually cancel the order during the cooling off period, but you actually became a customer of this other company even if it were very brief, the alternative is that it’s a coincidence that these calls happened in that 2 weeks between you raising the order with the other company and then cancelling, even though there was nothing special about that period , so that seems very unlikely.
No ISP is supposed to contact you , simply as a result of receiving the notification that another company is taking over service , ( they are not supposed to contact you offering a better deal to convince you to stay because you have started the leaving process ) , but it’s allowed , if you contact them after starting the migration yourself , so why did you contact BT after you had already signed up with another provider, or did BT contact you after they had already sent the ‘sorry to see you leave’ communication ?
You are in an awkward position, if you never reported ‘crossed line’ fault , then your line was never connected to another address where someone else ( a total stranger) may have made calls on your ‘line’ , it would also be odd that they would realise they temporarily had a different phone number and thought , ‘right , let’s make £500 worth of premium calls , as they won’t be on my bill ‘ ,
If the migration never happened , there was never a period where your line was connected any differently to how it was before you started the switch you subsequently cancelled ( unless you didn’t to that in the cooling off period ) , so nothing really happened to your line during this period.
The cynic may allege that calls were made on your line during this 2 week period ( perhaps not by you but someone with access to the master socket ) hoping that after the migration the calls would never be billed for ( they would , they would be on the final bill ) or that the old company, because they wouldn’t be supplying service anymore, wouldn’t be able to suspend service for non payment , and by not completing the switch , you stopped that ‘plan’ working.
Finally, does any family member , friend, employee , visitor etc. have access to your ‘line’ as it’s more probable that not , that the calls were made on your line , ( because nothing ever changed ) the abandoned switch to another provider didn’t physically change anything, even temporarily, and you never had a reported fault, so if you cancelled before the new company took over , then really its the same as if you simply had unexplained calls on your bill , the cancelled migration is irrelevant, unless someone thought it was a good time to make these calls that they thought would never be ‘billable’.
