For instance you could be excused based on your employer sending a letter that it would be inconvenient to their business if they lost you, etc.
So in practice, you can probably wiggle out of it if you simply don't want to do it, by finding a suitable excuse.
Another system where random service is still commonly used is military draft. That seems significantly more hardened against dodging (since the cost on the individual of going with it is drastically higher).
So generally, it seems that where current societies do use random sampling to select people for service, there is always an element of compulsion, but how "hard" it really is varies.