Child benefit charge HICBC

I’ve been in contact with HMRC since been caught in the HICBC since 2019,i as many other people didn’t not realise about this charge and that was an honest mistake as I’ve been PAYE since leaving school. I arranged a accountant to fill my self assessment as I didn’t want to make a mistake,my original discovery assessment was for nearly 4 k,there was a mistake made by HMRC which lead to a double assessment which then increased the the amount to nearly 9k with extra penalties etc. This took nearly 6 months to resolve with nearly 50 phone calls to HMRC,my question is why am I responsible for this mistake and been hit with nearly £1500 in penalties and interest I’ve payed nearly £4300 but I find it wrong that I should pay any more of the charges due to HMRC mistake in the double assessment. Also you can not pay via credit cards I’ve had to borrow money from family to pay of this bill,and I’m seriously struggling to pay of this remaining balance HMRC refuse to make reasonable payment plan with me,and yet I’m still getting late payment fees and interest. The stress and anxiety this has caused me over the last few years is really leading me into a dark place,I’ve worked all my life payed my taxes support my family and 4 kids never claimed of the system apart from family allowance and now in a spiral of debt this seems so unfair yet to couples can earn £49.999 each PA and keep all of there family allowance something is very wrong in the system.

I doubt you will get much help about a government policy change here but perhaps it's something to raise with your MP?

Thanks for the reply that’s not a bad idea