In this case, just calling the commlink would not be enough to start a hack on someone due to commlink calls, emails, etc. being handled as a "Data Request".
In 2070, most of the traffic through the Matrix is caused by data
requests. People want to read their favorite website, watch the morning
news, or grab the latest episode of Karl Kombatmage. AR users want to get the
profile of the person sitting at the bus station, read the history of an exhibit,
or get the price tag of some item. Nodes want to read pieces
of data out of databases, synchronize timetables with other
nodes, and distribute data. Even phone calls and simsense
broadcasts are packaged into requests.
Nodes send data requests to the Matrix, and other nodes
answer with the needed data package. Most data are protected by
access rights, and requests are only granted if the proper access
rights conditions are met (see Accounts, p. 52).
A data request is not enough to hack someone since hacking requires a 2 way communication link, AKA a "subscription".
In order to hack a node, you must either be within mutual Signal range of the target node’s
device or have an open subscription with the node through the Matrix.
You can get a subscription simply by logging on to the public access area of the commlinks node, assuming it is actually connected to the matrix, and
is operating in either active or passive mode. Note, however, that most Runners & Johnsons, and most any corporate node worth hacking, will be running their node/commlink in hidden mode, and or possibly even have public access completely disabled. as well as generally using disposable commlinks to firewall their calls so that if you get a commcode or access ID, its probably not the real thing, or at least sends you to a node with no real data on it.
If the commlink/node is operating in hidden mode (which it probably is), you must be within mutual signal range and detect his hidden node before you can start to hack him.
Now, assuming this is some joe shmoe or a green johnson, it is possible that you got the real code, and they are not in hidden mode, in which case, they are pretty damn easy to hack. All you would have to do in this case is:
1. call them, and then, while talking to them,
2. run a trace. Once the trace is complete, you would then
3. log on to their public access area, and then
4. begin to either probe or hack on the fly to create a "valid" account on the node.
5. log on to new valid/fake account. (done automatically when you hit the hacking success threshold).