Paying my final post office bill when I am moving?

I didn't tell post office that I am moving because I skipped out of their termination fee because they were raising their prices at the start of november, this allowed me to perfectly time my termination for the end of the month without incurring a termination fee.

I was also getting legitimate line drops every day or two so that is also a geniune grievance.

I still need to pay my final bill though but I didn't tell them I am moving house as I thought they might renege on it and charge me the termination fee after all if they thought I just did it to avoid the termination fee, or can they not do that now they have already agreed to it/is it very unlikely the phone assistant/whoever would care?

I still wanna square up with them but if I don't give them my new address they are going to post to the address I am moving from and I have not setup mail forwarding here.

I was on direct debit anyway so it will just be taken automatically won't it and the paper bill is just a physical confirmation of what I could find out if I rang them up right?

I would check it online but even their website is awful; the bills section requires flash which is deprecated and does not work for me but I can see the summary on the dashboard.

Thoughts?