A lot of important and integral scenes in Air happen _________ the phone.

• Over/on the phone (idiom)
Meaning: by calling on the telephone.
Example: You can order a pizza over the phone.

• সাধারণত Phone শব্দটির পূর্বে  by বসে।
- কিন্তু 'the phone' এর পূর্বে over/on বসে।

• তাই নিয়মানুযায়ী সঠিক বাক্য হবে -
- Complete Sentence: A lot of important and integral scenes in Air happen over/on  the phone.

• By phone: The company can be reached by phone on this number
• Over the phone: You can arrange a meeting over the phone.
• On the phone: She has spent hours on the phone in recent weeks.


Source:
1. Cambridge Dictionary.
2. merriam-webster.