Fast mail envelope purchase

I was at hazyview post office and I'm dissatisfied.I wanted to buy 2 A4 fast mail envelopes but I had to join a que which includes people who are waiting to get their sassa Grant's.The que was not long but for them to service 1 customer it takes 5 minutes or more.So I ended up leaving as it was hot in there and I didn't understand why I should que that long when buying fast mail envelope takes even less than a minute.