Income verification Letter

I got excellent service from all the people at Old Mutual after my mom past away

The policy was paid out within 2 weeks BUT then the fun started

FNB froze all the funds paid out to me and asked for an Income verification letter to see where and what the money is for (this is ridiculous too because it is showing as Old Mutual payment)

I received the money on 17 April tomorrow will be a month and I am still waiting for the letter and cannot access the money