Cool down cancellation not accepted.

Hi, I have recently renewed my contract (no device as I chose sim only). The day after, I decided against it, and sent an email to the retentions email address. Within the 7 days I got a reply asking me for some.additonal i formation which I sent immediately within the hour. A few days has gone past with no reply. I called the retentions department telephonically (********* long wait time) after which the agent told me the contract is active and I cant cancel anymore. This is unreasonable especially since there isnt a device in question and the response delay is out of my hands.