You must have misunderstood me. I didn't write that "will" is incorrect to use for the future action in general. What I stated, though, is that "will" cannot be used when talking about arranged / planned actions, which might be a temptation for an ESL learner. Consider this example:
Person A: Have you booked your driving test yet?
Person B: Yes, I have. I'm going to take it in June. I can't do it earlier because my grandmother is visiting us this week.
Will in both cases would sound wrong because neither of them is about spontaneous decisions.
Person A: Have you booked your driving test?
Person B: No, I haven't yet...I completely forgot! I think I will book it this week.
You must have misunderstood me. I didn't write that "will" is incorrect to use for the future action in general. What I stated, though, is that "will" cannot be used when talking about arranged / planned actions, which might be a temptation for an ESL learner. Consider this example:
Person A: Have you booked your driving test yet?
Person B: Yes, I have. I'm going to take it in June. I can't do it earlier because my grandmother is visiting us this week.
Will in both cases would sound wrong because neither of them is about spontaneous decisions.
Person A: Have you booked your driving test?
Person B: No, I haven't yet...I completely forgot! I think I will book it this week.
In this example, "will" is correctly used.