You can add a minimum and a general maturity to all so called tariffs (a product of type 'Internet', 'Voip' or 'TV'). A contracts end of term shown on the invoice after executing the settlement run is determined by the assigned item. If you have multiple items with different types (and valid dates !) assigned to the customer the following order takes precedence:
Internet
Voip
TV
So if there's a customer only having a Voip tariff (no internet) the maturity of the corresonding Voip product is used to determine the contracts end of term.
It's important to say that if the Internet item is bundled with a Voip item and the Voip item was added after the Internet item then the Voip items maturity is used to determine the contracts end of term.
The TV item is only used if the customer neither has a Internet nor a Voip item.