WIC (cisco)

Dear friends,
I have heared that there is a limtation on
bitrates in the WIC in cisco routers.
One of my friend said that he can not send more than 128 kbps on WIC-1T , and she needs
to a WIC-2T which it can works with up to 2mbps .
Is it true ?
where can I found this technical information ?

look forward hereing from you.
best wishes