When do I call to end/cancel my contract if I have to give 30 days notice?

[GuestCustomer]

My contract ends 14th April and I don't wish to pay anything else after that date as I would be paying £65 despite my contract/phone payment ending, but I've read that they need 30 days notice to end a contract so when exactly am I supposed to call? If I call now to make sure it ends on the 14h April or 30 days from today, will they tell me to call back on the 14th April and give notice then as that is the day my contract ends or what? Why is there no option in the account to end it? Absolutely ridiculous having to call to end a contract when one can be set up without a phone call. 

Thanks

[MI5 · Accepted solution]

@GuestCustomer 

Notice is no longer required.

You can cancel anytime and you will just be billed up to your end date.

Guide: Cancelling Your Contract