Hello I will help you with your question,
There are three possible causes for this wobble, tire is separated, rim is bent, axle is bent.
Swap the rear tires and see if the wobble is now on the other side, if it is the wheel is bent or the tire is separated. If the same wheel is wobbeling the axle is bent.
The shop that balanced your wheel should have looked for a bent rim or separated tire when it was on the balancer. You can carefully run your hand around the tread and feel for uneveness or a lump then walk beside the wheel as someone drives slowly and watch the wheel for a bent place.
If it is bad enough to feel you should be able to see the problem with this process
Let m eknow if you have further questions about this