2005 Toyota Echo jerking when accelerating around round a b

Transmission problem
1985 Toyota Echo Automatic 100100 miles

since I had a service done last year, my car has been jerking when I accelerate off from going around a roundabout or accelerating quickly up a hill. It sometimes does it when picking up speed from traffic lights too. It's fine at higher speeds and changes gear smoothly when driivng along. Last year when I went to pick my car up from service I had to go return later because he said the apprentice had drained the tranmission oil and he needed more time to get it back to me. I had it serviced for 100,100km this week and so oil levels are fine. Not sure what to do and whether I should get it attended to. Any suggestions about what it could be and what I should do? Thanks!