Here is how to transfer airtime from one Airtel line to another:
You must change the default PIN "1234" before you will be able to transfer airtime, in some lines the default PIN is 1111.
To change your pin, Send a text message in the following format to 432:
PIN [space] 1234 [space] NEW PIN. For example, if you want to change
your PIN to 4321, send “PIN 1234 4321” to 432. You will receive SMS
confirmation from 432 that reads: Your New PIN is 4321.
Now, to transfer your airtime, Send a text message in the following format to 432: 2u [space] phone number [space] amount [space] PIN
For example, To transfer N1200 worth of airtime to subscriber
08021234567, the message will be: 2u 08021234567 1200 4321. You will
receive an SMS confirmation from 432 that reads: “You have just sent N1200 to 08021234567”