We buy cars holding up closure of finance account

I sold my car to We Buy Cars on February 13th, and We Buy Cars paid Wesbank directly on the same day. However, neither me nor Wesbank received any proof of payment. Wesbank has been requesting this proof for the past week to finalize my account. I messaged the agent on Tuesday, asking them to please email the proof of payment to me but nothing has been sent. My husband called the agent this morning to request the proof of payment, his response was, "I will TRY and get it from Head office." My husband then called the call center and was told they would have to speak to the agent and then the line went dead. No one bothered to contact me back. Why is it so challenging to get proof of payment, surely the Bank should have been sent a proof of payment and surely I should have received it as well without having to ask?? We Buy Cars is obstructing the finalization and closure of my my account.