Airtel And Vodafone — validity of recharge

I want to draw your attention toward loot of telecommunication companies. They provide 28 days validity and 100 mb data on compulsory recharge of rs. 35.00. But they are not providing data and most interesting is they send reminder massages before 5-6 days of validity expiration. When we recharge before expiration of validity they start fresh counting of validity of 28 days from date of recharge and if we dont recharges before expiration they deduct amount from balance automatically in midnight.in this practice we never get validity of 28 days.