You can define a free trial period for a certain period of time which you set. The contract which is assigned this payment period will not have to be paid during that time. After the trial ends, the contract will be treated as a regular contract.
Free trial end reminder
You can also remind the customers about their free trial ending a number of days before it ends, and you can select which template to use to notify them. If you dont want to use the standard template for that, you can create a custom one of type Product, then you can select it here.