Going through this too (and went through last year). Contact OVO again to let them know and get a case number. This will help with chasing updates. But it can take a while as the suppliers chat to each other (and ignore the customer!). If they take over a certain time laid down by Ofgem (sorry don't have link to hand) then you are owed some compensation. 

However like I said it can take a while to sort (months for me) and I ended up going to the Ombudsman. So document everything! However I wasn't left with electricity so you should not have your gas cut off. 

Hi @caggymcc,

I’m sorry to hear this.

Sometimes we receive a request for us to switch your supply away from us in error. Whilst it’s quite rare there’s a few reasons this may have happened:

• Human error - someone may have entered your address details when applying for a genuine switch
• Fraud - very occasionally fraudsters may use your details to apply for an energy switch (if the details held by the other supplier match your details it might be worth contacting your bank and checking your internet security procedures)
• Mistake in your address listing on the national database - If way your address is listed is unclear or incorrect this can cause issues switching - check out this topic for more advice in getting this corrected.

If you receive an unexpected leaving email, contact our Support Team to let us know you don’t want to go. They can put a stop to the impending switch and find out which supplier’s making the request. You’ll also need to make sure you let them know that you don’t want to switch to them as they may reattempt the switch.

This thread might also be useful: