Debt management firms provide a service that initially involves negotiating an agreed monthly payment with the people you owe money to (your creditors) on your behalf, based on what you can realistically afford. You (the debtor) will then make the payment to the debt management firm and it will distribute the payment equally between your creditors in proportion to the amount owed. It is an informal (not legally binding) agreement, so your creditors can still call and write to you. Also, there is no guarantee that any charges or interest will stop - even if you make all of your payments on time and you will have to make the monthly payment until the debt is paid off in full, no matter how long that takes.
Example
Debt total = £25,000
Amount you can afford to pay = £200 per month
£25,000 / £200 = 125 months to pay debt.
125months / 12 = 10.4 years to pay off debt (without any interest or charges being added)