Missing emails

Sent a request to old mutual on 18 September 2017, was told that my request would be handled in 5 working days. More days have passed and no feedback. I call in and I'm told my request was never received. I forward my original request but they want more proof in order to escalate the matter. There was no receipt. I resent my request today,no receipt. I send another email immediately after that and only then I received a receipt. So now I have to wait again. Clearly there is something wrong with their email system since I only received one receipt for two emails sent. I don't want to wait since this is not my problem.