Use of present vs. future tense in example

Hello.  The following example in this lesson threw me off:  "After the party we will call a taxi" (Despues de fiesta llamamos un taxi).  My question is why was the present tense ("llamamos"), and not the future tense ("llamaremos"), used here?  My guess is that the future time is very short (i.e., right after the party).  If this is correct, is there a general rule for a given time frame that would require use of the future tense?  Thank you for any clarification.