Along the film advance lever side if the camera there is a lever or pin in the gap that the back fits into that releases the film counter when the back is closed. When pressed its not fully releasing the counter mechanism so its not going back to the start point, its bent so that the back is not pushing it in far enough to reset the counter or the counter is not correctly functioning internal of the camera.
When you open the camera to change the film inspect the top grove of the body that the lip of the back fits into. The lever/pin should be parallel to the top plate of the camera. Close the camera back and check the film counter, it should be blank or a dot showing, not at a number.
If the lever/pin is bent or the counter does not reset to the start point take it back to the shop that serviced it.