Actually there are quite a few different indoor bikes used for indoor cycling that micro-adjustment capability and not just the push-pin holes.

I would ask your instructor to check your set up. When you are in the saddle and your leg is extended toward the bottom or 6:00 position, foot level, you should have a very minimal bend in your knee. Then, leveling your feet (three and nine o'clock positions) have the instructor check (either eyeballing it, or better yet, with a plumb line) that the forward knee angle, lines up with the pedal spindle or the ball of the foot. Then, pedal a few times to make sure your hips aren't rocking in the saddle.

You might even try visiting some other clubs...try out different bikes....they aren't all the same. Neither are the instructors.

I always set up new participants, and eye-ball everyone's set-up before class and I have three soon to be four indoor cycling/Spinning certifications, all of which specified how to set up clients on the bike. It's unprofessional not to pay attention to that detail.