Looks like nobody has idea regarding that and it is expected as "Airtel is totally Unpredictable wrt prepaid and reaching their CC executive is like catching the Unicorn. So I decided to bite the bullet and find it myself.
[1] Asked the Airtel store guys, they have NO IDEA.
[2] I tried Airtel Thanks app, there is NO info regarding recharge queuing at all and their Chat Bots are good for nothing, as expected.
[3] Then asked my recharge store friend, he said "with Airtel it is always over-writing current plan" and when I asked about my friend's recharge queue, he was amazed, but still said what I really don't want to hear, "I will recharge for you, but you should not ask if new plan starts immediately".
[4] Later I looked for ways to connect Airtel CC from other number and I got "98941 98941" as number for
calling CC from other number for TN Circle. (I don't want to call from my dad's number and I have Airtel Postpaid number). After typing some 30 something numbers (incl twice my dad's number for confirmation), I got one CC executive today morning @ 6AM. I think he is working from home, as I heard the morning alarm / crowing sound of Rooster in background. Man, he has got all the necessary details, I was looking for and I am submitting below:-
- You can queue only the UL plans WITH DAILY data over Daily data plan.
- It doesn't matter if its 1GB/day or 1.5GB/day or 2GB/day. You can mix and match any daily data plan over any other DAILY data plan. It will be queued.
- You can queue more than two daily data plan (over daily data plan)
- If you try yearly UL plan over daily data plan (my case), yearly plan gets activated immediately.
- Queuing Yearly UL plan over yearly plan will work as usual.
Conclusion:-
So from my experience, early morning is best time to catch the CC executive, Airtel allows queuing of multiple recharges of Daily data plan of any value / any validity / any amount of daily data & don't mix daily data plan with yearly data plan, latest plan will get activated.