Standard Bank card declining informing insurficient amount, while there is enough amount in the account.

My standard Bank cheque card just declined informing insurficient funds, but when I checked on the standard bank app there were more than enough money available. I emidiately called their telephone banking to check and they asked if my card had expired, I told him that my card is expiring in 2023. After that I was asked to hold as the person who was assisting me didn't find anything wrong and he also confirmed that there was available funds in my account. Another problem is I had to wait for 20 min on the phone, using my airtime and waiting to get access to my own money. But come month end, they are so quite to debit money into my account for this kind of service. After this call I went to the same machine that initially declined and the transaction went through. But they insist the was nothing wrong.