Accounts department not doing their job

Their internet service from the IT guys is great and they always answer calls. As for their accounts department have left a bitter taste in my mouth. I canceled my services due to relocation and sent the notice well on time. Fast forward to Now I have been struggling to get hold of the accounts department for my deposit which is overdue. 25 working days have passed and I am still waiting. If this year ends without my money being back I will be forced to take legal action. Whatever the cost I WANT MY DEPOSIT BACK.