Funny + Frustrating Experience at Post Office

I went post office today to send something to my customer. When I arrived, nobody was at the two opened counters so I decided to simply queue up at one of the counters. Then, an old staff told me to queue up at another counter and closed his counter. After waiting for 2 minutes, the old man came again and asked me to queue up back at his counter.

Well, this next part is the most interesting one...

Old man staff: Miss, RM 8.80 pls
Me: I wanna add 2 RM 2.50 envelopes too
Old man staff: You pay for this one first
Me: *Thinking* Why? You don't know how to use the calculator in front of you? Just press the calculator... 8.8+2.5+2.5 then you'll get the answer!!!
Me (in reality): Ok... *hands him RM 10 and he gave me back RM 1.20*
Old man staff: Ok... what is it that you want?
Me: 2 RM 2.50 envelopes... (I have to repeat twice before he got what I want and handed him RM 5)

I know he can avoid his own confusion by separating the transactions but this is definitely inefficient! It's as if I have to queue up twice to buy different things!