Help! Undisclosed bank accounts??

I had a message on my Universal Credit journal last week saying I had a telephone interview because they believed I might have undisclosed bank accounts. I genuinely don’t, so at first I wasn’t too worried.

During the call, I went through all the accounts I do have (which they already seemed to know about), but the interviewer kept asking “is there anything else?”. I said no.
She then told me they had information showing I supposedly have NINE different accounts across 3 banks that I’ve never declared. She could only tell me which banks they were with and how many accounts were at each bank, but no account numbers or other details, because I was saying they weren’t mine.

After the call I contacted all 3 banks directly, gave my full details, and every single one confirmed they have no accounts under my name, date of birth or address.
Has this happened to anyone else before? The banks confirming there’s nothing there is reassuring, but it’s still really worrying that I was told these accounts exist in my name and that it’s affecting my UC claim.