I first installed the md300 debian package ... which didn't work with mobinil.
But wiht some changes to the wvdial config (see attached wvdial-mobinil.conf) I was able to use the MD300 modem with mobinil 3G internet.
With the current price 1Mb is 0.30 EGP, so such prepay card. So be carefull which sites you visit.

The configuration (taken from the example config of the md300 package, generated with md300 --init) needs to be changed a little to make it work with mobinil in egypt.

Configuration for wvdial to use md300 with mobinil

[Dialer Defaults]
Modem = /dev/ttyACM0
Init1 = AT+cfun=1
Init2 = AT+cgreg=1
Init3 = AT
Init4 = AT &F &D2 &C1 E0 V1 S0=0
Init5 = AT+IFC=2,2
Init6 = ATS0=0
Init7 = ATZ
Init8 = ATQ0 V1 E1 S0=0 &C1 &D2 +FCLASS=0
Init9 = ATZ+cgdcont=1,"IP","mobinilweb"
Password = 
Check Def Route = 1
Phone = *99***1#
Idle Seconds = 0
Modem Type = USB Modem
Stupid Mode = 1
Compuserve = 0
Baud = 460800
Auto DNS = on
Dial Command = ATDT
Ask Password = 0
ISDN = 0
Username = mobinil 
Password = mobinil
Carrier Check = off

[Dialer mobinil]
Stupid Mode = on
Username = mobinil 
Password = mobinil
Auto Reconnect = on
Phone = *99***1#

Some things in this config are double, and I guess unneeded. Unfortunately while writing this I am now in Holland and am unable to check changes to the file. Please try and let me know.

References:

• http://www.niclabs.cl/entel/MD300/UbuntuDebian%3DENG.html