Excess Refund - No Feedback

I had an accident with in 2016 whereby a third party drove into my vehicle whilst stationary in traffic. IUM settled my claim and then proceeded to do a recovery against the third party. According to the legal team at IUM, the recovery was successful in January 2018 which means I should have my excess refunded to me. After numerous emails and phone calls, my query is still being ignored. The amount is not much, but how much money are they accumulating by not refunding the client's excess once a recovery is successful. I am really upset with the lack of response from IUM.