Disconnecting from GPRS?

I am using wavecom modem in vehiche tracking. It sends some data to server port via GPRS. But I can’t avoid modem to disconnect while passing from one base station to other.

I am using ADL library, Open AT 3.02,

Is there any special AT command to avoid disconnecting?

I am want to make like youing in the past. But I isn’t understood, you can help Me way make ? I thank you much.