And the saga starts drawing to a conclusion.
After 44 hours, I finally got put on with a VM agent via their WhatsApp chat. Having said I wanted to cancel and not haggle, he continued to try to haggle with me through about 4 or 5 more exchanges before I could get him to believe what I said the first time: I really wanted to cancel, and there's no deal to be done. As others have noted in this and other threads, these guys at this level have no control over what happens over at O2.
Therefore, having won this round, I went over to O2 live chat. I have three lines on Volt Benefits, and – unlike the experience of others here – O2 *were* willing to cancel penalty-free the line they consider the main line. They others they said would have to stay or take the cancellation penalty. Problem was: that's not the line I consider the main line. (I could have lived with keeping the other two if I could get my main one free.)
I protested that they were all on Volt, so should all be freed. Then I asked if I could swap two of the numbers as the main account number so I could free up the one I really wanted. They said no, but let me escalate that to a manager quickly. The manager said there wasn't anything he could do about it directly, but offered me a fudge: that he could hand me over to contracts, they could swap my long-term contracts for a 30 day rolling contract, and then I could cancel and get PAC codes once that was actioned.
Sounds very weird to me, but I double-checked that he was saying what I thought he was saying. Then let him hand me over. Practical upshot: after going through a really long-@ss legal script, I got all three numbers moved over to 30 day contracts – checked several times that there wouldn't be a penalty for changing contracts – and now I'm just waiting for that to be processed. I was given order numbers, so I can follow that up if something goes wrong. And I've done all of this in writing, so I can have a record to follow up with if it all goes pear shaped.
This solution is more on the lines of "pragmatic" than "principled" – i.e., they gave me an unexpected workaround, rather than waive the terms of the contracts – and it may or may not cost me an extra bob or two. But, assuming what happens is what they promised, I'll be out of the contract without penalty.
I'll let you know if it doesn't work or if I have to do any more arguing. But, for now, I'll say it was time-consuming, but simple enough.