New sim or new number cheaper?!

[#1]

I am already a Plusnet customer with a rolling 30 day contract @ £6 a month. I want a new mobile number.
What is the cost to change my number?
Is it cheaper to order a new sim and cancel my existing one?
I’ve noticed the same £6 deal no longer exists and is now £8!
Looking for the easiest and cheapest way to get a new mobile number.
Thanks.

[#2]

Hi there Emski, it's a charge of £25 to change your number. 

Please feel free to send over a PM to me with your mobile number and your full name and I'll check what deals we're able to offer you. 

Adam