Raspberry Pi UMTS / LTE Stick with VPN to Fritzbox 

Huawei USB Stick E160E with Telekom / Congstar SIMcard.
VPNC establishes over wvdial a connection to my noip.me fritzbox.
WVDIAL Config for congstar:
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[Dialer Defaults]
Phone = *99#
Username = "t-mobile"
Password = "tm"
Stupid Mode = on
Dial Command = ATDT
Modem Type = USB Modem
Modem = /dev/ttyUSB2
Init1 = ATZ
[Dialer umts]
Carrier Check = on
Init2= AT+CGDCONT=1,"IP","internet.t-mobile"
ISDN = off