I am afraid this appears correct. If you were in arrears of £492 and this sum was due and outstanding and you were going to pay £30 a month then this could be a breach of the original agreement.
Unless it was a credit card where you could pay £30 a month and this was the minimum payment or more, regardless of whether the firm had agreed to you paying a lower sum, it will be recorded as adverse credit information.
This is because you had not adhered to the terms of your account.
You can write and make a formal complaint. They will investigate the matter and report back to you.
If they do not uphold the complaint you can then go to the Financial Ombudsman. They offer a free, independent service and can examine your complaint for free at:
That may resolve it for you.
Can I clarify anything for you about this today, please?
If you need anything further I am available for a follow up at no extra cost.