Airtel Broadband: Anyone faced problems with VPN and Wifi.

Question:
I have been using Airtel connection (RB Comtec modem) with my office VPN for quiet some time without facing any issues. Now I want to switch to WIFI. For this I will have to switch to the Airtel Beetel modem and a router. But the technician advised that I would not be able to use vpn once I switch to wifi. He said this happens because in wifi The router gets the dynamic ip instead of the system (in case of modem). Can anybody make sense out of this? Have you people used office vpn with wifi?
Is there a way out of this?
Answer:
I got installed Beetel 450 BXi modem installed on Saturday, just to find out that vPN will not work over this wirelss modem, and Airtel broadband and telephony services does not have any responsibility for providing VPN over wireless to its customer in Delhi/NCR regions. They want me to switch back to beetel 220BX wired modem....if i want to use my VPN...this is what told to me straight! told by the engineers.............it'll support the vpn provided by airtel though.