I think you are potentially being a little paranoid.
As stated, people ordering service, especially for an address they are due to move into rather than changing provider at their current address , can give an ISP the incorrect address details, or the ISP can , if the customer is a little unclear on the address details ( gives the wrong post code for example ) they can select the wrong address , these things happen.
The fact the Openreach tech was apparently speaking to the ‘customer’ whilst at your address doesn’t suggest fraud attempt made on you , after all , it would be a bit of a stupid attempt , if while talking to a scammer the tech is outside your address and you come out and ask what’s going on , this scam wasn’t exactly going to go unnoticed for a long time , an engineer knocking on your door and you say ‘ why are you here , you are at the wrong address ‘ ,
After you tell the tech ‘ I haven’t ordered anything from an ISP that uses Openreach ‘ the tech leaves , returning the job as incomplete, and if it were a scam , it’s now discovered, scammers don’t want you to know what they are up to , that’s why this is almost certainly a mistake not a scam , in fact if it were a scam , it’s probably the poor people the tech was on the phone to that are the victims not you , after all, they may have been sold a tenancy for an address , paid rent etc in advance for that address ( your address ) and the ISP has been unintentionally involved by the victim, unknowingly ordering service for your address , somewhere they will never be able to move into , but I think that’s also less likely than it’s a simple error over addresses .
How do you know it was BT that had arranged the Openreach technician visit , there are dozens of ISP that use Openreach , so what caused you to call BT and not call Vodafone or Sky or Talk Talk etc.
As stated , you were already provided with information that you shouldn’t have been given , even if BT were the company that the consumer ( in error ) gave your address to BT they are not going to discuss another customers details with you , after all I’m sure you wouldn’t want your ISP discussing your details with a random caller , but what makes you assume it was BT , did a parcel turn up at your address from BT but in someone else’s name or did you incorrectly assume it must be BT and you called them without any evidence that BT are involved ?
Frankly you are overreacting to what is probably a simple error caused by a confused consumer giving your address instead of the correct one , or the ISP that sent Openreach put the wrong address on their request for service, it’s not a big deal , OR send the job back , the ISP that raised the order asks their customer to confirm the address , the error is discovered, a new order raised for the correct address and the order that sent a technician to your address in error is cancelled, it’s no big deal
