Old Mutual suspended my account and they cannot provide me with a valid reason.

I have an old mutual account that I have been using for 11 months. I used this account for full 11 months with no hustles from old mutual. Earlier on this month this account was suspended and noone from Old mutual both branch and head office can provide me with the real reason for this suspension. At first I was asked to submit all proof of payments from all the people whom I've been receiving funds from and I compiled with that. Then I was told that they will be lodging an investigation till to date I have not received any feedback. Can they at least tell me what do I need to produce in order for them to unsuspend my account? I was referred to Old mutual by my friends and they are also disappointed by this as they spoke highly of Old mutual. This is disappointing.