Dear Ravi,
Form 15-G can be submitted only when the total income before availing deductions u/s 80-C,80-CCF,80-D etc. is below the maximum amount not chargeable to tax.Hence strictly speaking even if you are able to avail of some deductions under Chapter VI-A to bring the total income below the taxable limit,it would be a false declaration.
You need to pay any tax which is due as per your revised calculations.In case of any queries at a later stage,you can always explain that you had submitted Form 15-G based on last year's earnings and a reasonable estimation of any changes to them.Though you might have wrongly submitted form 15-G for non-deduction of TDS,by paying your correct tax you could minimise the consequences.