How to arrange transfer of service from present provider

I am with onestream and the service ends with them in about three weeks. I signed up with virgin and the form said that they would arrange the transfer. However the form did not give me an opportunity to provide a transfer date. As no transfer date was given I did not give final consent to the virgin service.

Meanwhile onestream have emailed me to say they have heard from virgin and they're going to charge me £241 for switching. Even though I haven't given consent to virgin for switching yet and have already paid for onestream up to the contract end date.

This is an absolute mess and it's really annoying because the virgin form said that they would sort out the switch. Apparently they're not doing this properly and telling one stream that I want to switch today  rather than arranging a smooth handover when the onestream service ends.

Does anyone have any ideas how to unravel this mess.

Cheers