more than 1 submit_sm being sent on same data packet

Hi!

I got an application where I got to send blasts of many messages as
quick as possible.

I'm having the problem that sometimes 2 submit_sm are sent on the same
data packet, and there the SMSC returns a Throttling error for
receiving the 2 submit_sm too fast.

Is there any way of preventing Kannel form sending more than 1
submit_sm on the same data packet?

Thanks in advance,

Juan