What will happen if I don't pay?

You will not be able to access calendar,reports and other functionality (plugins will be disabled), but your clients will still be able to book your services. If you are having a break in your business (and you had paid subscription), you can close all your working hours and leave your account until you need it again and then renew your subscription. If you have free plan you can also close all your working hours, but you need to renew your free plan each month so that your company does not get deleted within 3 months.