Integration Testing: When to Mock and When Not to Mock

When performing Integration Testing when is a good idea to mock vs not to mock. From my understanding Integration Test should test the complete integration of the system. So, if I am in-charge of UI, Logic Layer, HTTP Layer and Database then I can use the real call made out to TEST environment.

However if one of those calls needs to be on a third party server like AWS or AZURE and I don't want to pay for a test call then I should Mock out that call in Integration Test.

Is my understanding correct?