Same. I also booked on full payment on 31st July. Although I haven't inquired about additional payable amount yet. A few suggestions:
Question?
1) What city are you from and who is your dealer/showroom?
Suggestion:
1) Contact Suzuki directly and ask them if this is even the case or is the dealer playing you?
2) Get in touch with someone on this forum who had booked on full amount and has taken the delivery without paying the additional amount. Ask them for a copy of thier invoice or delivery document and go to Suzuki with that claiming that since others didnt pay, neither should you since you booked on full payment before price increase.
Let me know how it goes.