You bring up an interesting point, Albywind, and I believe you are correct. However, it's still good to keep in mind that, whether one uses "will" or "going to," the idea of the sentence is still a future tense idea. The best English writers try to switch time frames only as much as absolutely necessary, so having another way to refer to the future is essential. Spanish and English are alike in this way, and having the option of translating Spanish to either a "will" or a "going to" form allows translators to pick the closest translation of the rest of the sentence so that their translations are truest to the colloquial use of each language by its native users.
True (US native here)... In the States, at least, to "call" can also mean "visit", though I think it's falling out of usage; I mostly see this sense of the word on small business window signs: "We're closed. Please call again later!"
... Which brings me to the question I was originally going to ask - can someone tell me if "call" has this dual sense in Spanish as well?