Try and have a list of your creditors and aporix amount owed.
You would also benefit from knowing your income and your expenditure so maybe a list of direct debits ..utility costs, council tax, insurance, rent/mortgage etc. The more you have to hand tge more accurate they can assess you for an IVA.
Sharing from experiences of dealing with debt
There is a solution for everyone .... Just need to stay positive !
However go ahead with the call even if you haven't got all the information to hand. Best to get the ball rolling as soon as you can . Its quite a long process at the best of times !