Emmie...The can't do that without letting your know first.
Last week, I had a letter from Santander, advising me that as I hadn't used an old savings account for over 5 years, they were going to make it "dormant" But all I had to do, to keep it going, was to make any transaction of at least £1. .....in other words, put £1 in or take £1 out.
When I tried to do that, in a machine here in the village, I found out that my card had expired in 2014 !
I then went into Santander in town, put £5 into over he counter and they ordered me a new card, which should be arriving any day now.
The account only had £59 in it, and if truth was to be known, I had indeed forgotten about it !
Emme....has the bank written to you first ? Its unusual for a bank to that that without informing you first....perhaps you didn't recognise that letter, or mistook it for some junk mail, which is easy to do these days !