I have 7 year old twins whom are both disabled. They both are receiving social security benefits and

... there is backpay to be paid out. I received the first part of backpay for both of them right away and was told the rest of it would be given to me in 6 months from that date. It has now been 8 months from that date and I still don't have it. I've call social security the different times and nothing much has happened from those calls. Any advice on what I should do?