Sounds like a canny telephone agent threatening you with a roadblock to stop you cancelling. Don't think you'll be getting any call back from VM unless you have actually put in a cancellation.
AIUI, you can't have two VM contracts running at the same address so you have to coincide the end of one contract with the start of another. If you have switched with your partner before, you will know the drill of having to return existing equipment, get new equipment on the new service, loss of any VM email addresses and VM landline number if any of that has any relevance for you.
I would guess that VM has a record of names/service at your address so the agent may possibly have been able to see past contract switches between you/your partner.
Not too much point in comparing your renewal prices with new customer prices as new customer prices are for, well, ... new customers. Find out what the prices are for the alternative(s) you might switch to and use those to compare against any VM offer.
There are some advantages to the OTS process and also some possible disadvantages, mentioned below
https://community.virginmedia.com/discussions/chatter/switching-supplier/5613428/replies/5613447
Topics on here in the past few months have routinely described VM coming up with ridiculous first-time renewal offers. VM does not really seem to care too much whether customers stay or go and relies heavily on the fact that many customers will find the renewal process too annoying and difficult so will sign up again with VM with a sub-par renewal offer rather than having to endure the unhappy experience of trying to continue negotiations with VM or cancel and leave altogether.