Breaking up can be scary...
But cancelling with your current provider can be as simple as giving them a call or email.
If you're out of contract, you generally don't have to worry about the cost of cancelling your current service but you'll likely need to give around 30 days' notice.
Check with the provider to see how long you'll need to wait before exiting.
Watch out for them.
Check with the provider's customer services or have a look over their T&Cs to find out exactly how much it would cost to cancel your service.