you are taking 200 X 20 working day = 4000 msg (definitely not teenager quota)
Try:
http://www.messagemedia.com.au/business/pricing
p.s not affiliated in anyway.. recommendation only
"Fair usage Policy" will be imposed if you are using it for business and excessive sms.
8c is for local numbers (is a good price)
but around 2 or 5c if you let them use international channels (and numbers)
