Metro Water's enigmatic accounting

Follow the money if you can:

• Metro Water Services sent us a February bill
• We paid the February water bill on time for the exact amount
• Our March water bill arrived with current charges plus February charges MWS says are past due plus a late fee
• I checked our checking account and confirmed that our payment was sent to MWS on time
• I meet with customer service rep this morning and produce our last checking account statement that shows payment to MWS in February
• MWS rep tells me that MWS changed customer account numbers and they have since had problems like this
• MWS rep says that they cannot credit account for February payment until MWS accountants "research" where the money is
• I ask where the money could be if it was received from a checking account 1) under the same names and 2) in the same amount on the water bill (and even the MWS account number we designated payment to had the same numerals in the same order as the old number absent a dash and a dot MWS removed)
• MWS rep tells me that only the accountants know where the money is
• I wonder what I did to deserve losing about an hour of my life responding to MWS's accounting problem
• I continue to wait for MWS to tell me where they put our money

By the way, I took time to pay our March bill while I was at Metro Water Services, though I may not be able to confirm whether they actually applied the payment to our bill until the April bill arrives.