Ending with Plusnet but full month bill?

[#1]

Hi I am switching from Plusnet on the 27th January, but have I just received my next month's bill for 22jan-22feb and payment will be taken on the 22nd of January.

Obviously this is wrong because I will be ceasing my service with Plusnet on the 27th.

So what happens here? Do they automatically refund my bank account the difference or do I need to chase this up to get money back from this bill?

[#2]

You should receive a pro-rata refund within 21 days of the service switching - leave your DD open until you get it.