01923 968638 Negative Who called me from this phone number?

CityFibre installed our new Vodafone fibre connection last Monday pm, telling us to wait 15 minutes - 1 hour for the system to allow internet access. In the meantime, at 16:42pm, i received a scam call from 01923 968638 that happens to be from a Vodafone Watford landline though I didn't know it at the time. The caller claimed to be from Vodafone customer support, knew that I had a not-yet-working £25/month installation and proposed replacing the broken router with a reduction to £18 for the inconvenience. He took my name, address, date of birth & period of residence before asking for my bank sort code & account number so that he could change the direct debit. I queried his request, Vodafone apparently keeps bank details in a special folder. I queried his identity, he offered to send me an email (impossible since we had no no internet), text message (nothing arrived) and then offered some explanation about not having my phone number! I categorically refused to provide bank details since he'd contacted me and not passed my checks and asked him to forward details to the local shop. Apparently, his router sent from London would arrive next morning whereas the shop were on a different system, would take 3/4 days to respond and had already closed for the day. He called off, I got to the shop just before 5:30pm closing, they ascertained that the number was dodgy, provided the true customer service number 03333 040191 and offered to take up cudgels next morning if necessary which wasn't needed since it began working.