Do any of you use software to allow class participants sign up for group fit classes of limited size remotely?

We have a number of classes of limited size due to equipment limitations and at this time our front desk staff field calls from participants and write names on lists for these classes. This is often a problem as staff are very busy, there are numerous lists and frequently names are missing or written in for incorrect classes. I’ve seen some places use what I assume is software or internet-based systems that appear to allow participants to do this themselves remotely. Are you happy with the system you chose? Has it streamlined your process? If you use it, how do you handle participants who sign up and no-show for classes? Thanks!