Mother's Self-assessment - Tax Letter errors

I want to cry. Passed from one phone line to another. Right phone line - person didn't know much and then hung up on me. Have submitted online Self assessment- got letter from HMRC - wrong details. Re-submitted online again - got letter HMRC - wrong details with tax increased more than 3 fold. My mother has had a piddling amount of extra interest this year. HMRC have added £3,000 odd for tax on her pensions - which have already been taxed at source as figure shown in calculation later on. HMRC added on tax for a lump sum payment she didn't receive or ask for (they've made it up!!!). And they want £2600 odd for "balancing payment"(?) for 24/25 self assessment? Help line suggested it was a technical error and then hung up about the "Balancing payment" bit. I just want to cry... I should be spending all this time sorting out fixing things for my mother and looking for home for her etc....

Hi Rada,
We are really sorry you are having issues getting help with your query.
We would need to access the record to review this.
You can contact HMRC by phone or webchat for assistance here:
Self Assessment: general enquiries
Thank you.