There is no limit to the number of people you can send airtime to but there is a limit to how much airtime you can send depending on the country you wish to send to.
It is priced differently across the different countries as seen in the table below:

No, you will not be charged extra once you have purchased the airtime. On Mteja, you are not charged extra for airtime purchase regardless of the recipient's location.

Did this answer your question?