Option 1) Chalk it up to experience, and remember never to trust the words of a salesman.
Option 2) VM record many calls, but won't say whether they record all sales calls. You could make a Subject Access Request for all call recordings they have referring to you, but that can take up to 30 days. If there's a recording that backs your recollection, they will have to honour that, because any promises made by a company rep, that you rely on when entering a contract are binding, and form part of the contract whether written or spoken.
Option 3) Phone and cancel your VM contract since you've got a 14 day cooling off period, starting from the day the service is connected. When you get through to the team who'll deal with cancellations, they'll want to know why. Tell them (politely) and explain you'll happily continue with the contract, but only if they credit your account with however much "puts you right". Since these staff are also on commission, there's still an incentive to say anything to get a particular outcome, so you may want to investigate means of recording the call - if doing that, do some tests beforehand to make sure the method you use works and provides audible recordings. Obviously if they say "no, can't do that" then you need to decide whether you will follow through and cancel.
