[I can get logged in but after 30 seconds get logged off]

I can get logged in but after 30 seconds I get logged of, this happen nomatter which sim I am in or time of day .

is it possible that there is somthing set on my computer or could the type of telephone line affect it, I have a beta high speed line.

if i connect from another location with my laptop i can get in ?

please someone help 

many thanks