[asterisk-users] Newbie: How to remote test a call prolem in an Asterisk site?

[Lee, John (Sydney)]

I will be installing Asterisk in a few offices which I don't have any
colleagues over there to help me.
Let's suppose I installed Asterisk in such a site.  I tested it to my
satisfaction and I went back to my home office.
One day, a customer called me to say that he had a problem calling out
or something.
Is there any way I could test out the problem myself remotely (apart
from READING the message on the console when the customer tested) or I
just have to believe what the customer tells me?
Can anyone share their experience with me please?