With the sipgate API, you can make calls anytime to initiate calls, retrieve balances, and more. In contrast, sipgate.io uses a PUSH-API approach, where requests are sent from the sipgate.io servers whenever an event occurs (e.g., a new phone call).
While the sipgate API is free, sipgate.io is available as an optional feature within your sipgate team account, with packages starting at £0.00 for sipgate.io S and going up to £29.95 for sipgate.io L.
Account Administrators can activate sipgate.io through the Plans & Packages section in their online team account settings. The sipgate API and sipgate.io are complementary and can be used together.