"You have a call!"
Translation:¡Tienes una llamada!
Any one syllable word with an accent indicates that there is another word without one. Él-he, el- the; Sí-yes, si-if; qué-what, que-that. Of couse the last example brings up another group of multi-syllabic words with paralells without accents (all the interogatives with accents have associated relative pronouns without) You will notice that the accent in these does not affect pronounciation, it is simply a writing convention to identify the meaning. Tú and tu (you and your) is just one case.
Yes, you could say It. It is also not very usual. You could say that when in a group, you're saying several things. That's when you use the pronouns, to emphasize the person referred.
Tú tienes que sacar la basura, tú lavas el baño y tú lavas los trastes. (refering to three persons in the same place).
No, tiene is the appropriate verb with the noun llamada when it means phone call. See definition 2A
Of course using ustedes surprised me a bit, but it almost always does for something like this. But in this day of business meetings taking place among many people remotely remotely over the phone it makes more sense.
OK. When I first read your post I thought you were questioning whether tener una llamada was a valid expression. If you are just questioning the Ustedes form, it certainly is more unusual. But, as I say, we now live in the age of conference call. Whether it is all together in a conference room talking over one of those those strange small spaceship like sound stations or a video conference, or people sitting at their own desks on their computers or smart phones on something like Go To Meeting, many times you will have many people in one office on the same call. In that situation ustedes would be correct