If it ran properly before the service, TAKE IT BACK!
They've inadvertently done something wrong.
If it ran poorly before the service take it back and ask for a compression test and all the items checked that mnl suggests etc.
Are there any warning lights?
What does the rev counter and speedo read?
Is it going down the gears?
Did it merrily sail up the same hill with the same weight in it last week, and now it wont?
Has the problem developed over a short or long time?
I'm a firm believer in "If something suddenly goes wrong- check the last thing you did", so as Jymner says, the service may have left a pipe off or a rag inside the air cleaner......
However, my crystal ball says that the catalyst is partially blocked and limiting gas flow