Problems with First Utility

Sunblind_Duck

Some months ago, my daughter changed supplier and left First Utility. A few weeks ago, she received a refund of overpayment, £196. She has now received a demand for £98 without any explanation or breakdown. When she telephoned the company and requested a detailed invoice, the lady on the other end said that this would entail a charge of £3. She also threatened to send in debt collectors. Can they treat customers in this manner? Surely, if the mistake is on their side, they should not be able to charge for sending a bill.