I have to stick to the operation of a Fritz! Box 7390 bought by AVM. It is one of the sticks that are tested by AVM also for calls. It's not about IP telephony, but "real" mobile telephony. It is used with a SIM card simquadrat. Both phone and Internet work very well with the stick. Inner half the last 6 months did not reveal any problems. The configuration on the Fritz! Box is a little confused. The stick has to be activated in the "Internet" menu. Only then can you enter it under "telephony" in "My numbers". This is from thing of AVM and can not be attributed to the stick.