how does anything change by charging for 3 6 months in one go? they are taking 3K (2K is refundable though i assume?) at the time of connection installation. so it's not like people would get connected. use it for one month. and then stop renewing! this would only happen if they know that their services are going to such so much that people would not renew after one month lol.
i mean seriously. if you are worried about network abuse, at least have bandwidth limits starting at 1TB per month.
most of the data people consume these days is from services that can be peered locally so data transfer cost is very low.