Letter from HMRC today saying I've underpaid my tax for 20/21 season by £52

The letter said I was in receipt of 1000's of £'ssss from income from a savings plan.

Hmmm I telephone and wait n wait n wait. Geezer answers and takes all the info and says Ohhh hold for a moment. I gets cut off.
I ring back and have to wait even longer.
Do I have to start from the beginning or did the previous chap make notes?

Do you want my phone number in case I get cut off again.
No he said as he has it and read it out correctly.

Going over it all again was doing my nut in so I said please investigate and call me back because being on hold on both of the calls and listening to that music has done my nut in and frazzled my brain.
He chuckles and says he can give a written response
Yes I will give you my email i said
No he can't email - apparently
I have a password to recall when he calls me back on Monday

Life's too effin hard these days