Council Tax Debt - collection agency

DebbieT69

My daughter moved into a shared flat mid March 2019. She received a council tax statement in joint names for 2019-20 and a notice asking for half a month's council tax for the part of March since they had moved in. My daughter paid this in full for March
She then received another notice for 2019-20 and notice for March 2019 in just her name, smaller amounts - she paid the one for March (Again!)
She didn't really understand the process so when she didn't set up a direct debit she waited until she got reminders, then paid the amount on the reminder. This didn't match the monthly amount she was expecting as shown on the notice for 2019-20.
The last reminder she got was in June, she hasn't heard anything else from the Council but received a letter from Scott & Co debt collectors mid August to say she owed them the balance for 2019-20 plus 10%.
As far as she knows her flatmate has applied for a student rebate and therefore doesn't pay anything - does this mean that my daughter is responsible for all the council tax for the property?
Joint amount was £177 per month, single amount was £133 with a discount, sounds to me like they give her a single person's discount on the full amount, shouldn't it be half the amount of the property (with no singer person rebate)?
She's been trying to get through to council on phone but I've found an Appeals form online that I think we can use, would rather she could clarify with a person though.
She phoned Scott & Co and was taken aback that they didn't go through and GDPR with her, just asked for her card number and said she HAD to make a payment online today before she could set up a ddm.
Is there an ombudsman we can contact about the debt collection agency to complain if nothing else?

CIS

She didn't really understand the process so when she didn't set up a direct debit she waited until she got reminders, then paid the amount on the reminder. This didn't match the monthly amount she was expecting as shown on the notice for 2019-20.

Reminders would only not match if either a revised demand notice had been issued or monies had been paid that part paid the instalment (hence a reminder asking for the missing amount).

The last reminder she got was in June, she hasn't heard anything else from the Council but received a letter from Scott & Co debt collectors mid August to say she owed them the balance for 2019-20 plus 10%.

Either a 1st/2nd reminder was not settled in time or a third instalment was not made as required. This then leads to a summary warrant being issued and an application being made to sheriff's court for a liability order.

As far as she knows her flatmate has applied for a student rebate and therefore doesn't pay anything - does this mean that my daughter is responsible for all the council tax for the property?

In most cases, yet.

Joint amount was £177 per month, single amount was £133 with a discount, sounds to me like they give her a single person's discount on the full amount, shouldn't it be half the amount of the property (with no singer person rebate)?

No, the discount is only 25% of the total amount in this case.