An monthly cost increase and change to contract just in one day

I called Virgin yesterday (05.04.24) and the agent added a landline rental to my package. She told me that the monthly cost is £31 and there is a one-off cost of £35 for the phone. I agreed with the changes. Then she sent me the contract, I reviewed and confirmed happy to go ahead.

 

However, all of the sudden this morning I received a new email and Virgin increased the monthly cost to £xx. I really don't like this because agreement should be agreement. I clicked a speaker button "Contact us" on the bottom, which brought me to send an enquiry to <theteam@mailing.virginmedia.com>. However, I immediately received a Failure Notice after sending the enquiry.

 

I called the customer team again and they don't know how such thing happens either. They think it may be an automatic price increase notification email sent by Virgin and my cost should be still £31. However, after hanging up the call I thought it shouldn't be like that because the email also includes a new contract, which is different from the one received yesterday.

 

I don't want to waste more time speaking to the customer service. Can anyone tell me how I can completely resolve such issue? Thanks.