Freebie subscription is causing 'payment' problems

I was given a free subscription for (I think) 3 months - it was about CC and 100 GB storage. This was totally useless and unneeded because I already have/had a subscription of the same (I am admin of our school's account and moreover have one of our three teacher/student subscriptions which I renew each year with a code). Now, the run-out freebie subsc. is causing problems because there was no payment method attached to it (obviously) and now it's on red alert - "payment problems!"! I cannot enter the subscription to 'cancel' it as it's ended - and I never booked it in the first place.

This is really annoying as the 'missing payment info' causes an alert in the system which leads to me not being able to use/enter my profile to the full.

Steffi