Business account closing refund

We have received two bills showing that we have a credit coming back to us for a multi-line business account that was closed in January.  Everything I could find online said it could take up to 60 days, that time is up on March 19.  However, we wanted a verbal agreement to make sure that check will be coming.  I called several numbers several times and spoke to several representatives.  They kept saying it was not their department and giving me phone numbers I had already called, who had already transferred me to them, and back to the other numbers I had already spoken to.  Nobody seemed to know who should be able to help with a closed government business account?  Because we are a non-profit government business, you can imagine how important it is to finalize the paperwork for the balance we have coming back to us in a timely manner.  We have board members, an accountant and auditors to answer to.  If we don't receive a refund check by March 19, who do we contact next?  Thank you in advance for your time and assistance.