Yes it is perfectly possible for an ISP to do this. It is also perfectly possible that it is the result of some sort of "automated" process.
These days you will not get very far by going direct to Ofcom in the first instance. You need to commence the complaints procedure that your ISP must (by "law") have in place to deal with complaints. The ISP must also have signed up with a dispute resolution service (such as Otelo) which, after allowing the ISP time to resolve the complaint directly, you can escalate the issue to.
If/when you do get to esclate then there is no cost to you in doing so, but there is a cost that the resolution service will charge to the ISP. Hopefully, that in itself will encourage them to see sense and sort the matter out if they can.
Hope this helps.
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