As a general rule, signal cables do not carry an electrical charge UNLESS something is VERY VERY wrong (I've seen it happen when a metal desk was on top of an electrical cable, and wore through the insulation. Since the signal cable (in that case, a co-axial cable TV cable) is GROUNDED, you'd get a shock if you touched the cable, and the desk, together. But that was really really weird.
If you're using an old-fashioned telephone cable, it might be possible to get a tiny buzz of a shock (like from a 9 volt battery) if you're touching the wrong connectors at just the right time when someone calls the phone, and the phone company sends out a ring-charge.
In your office, the only wires that can shock you, are ones that lead to an electrical outlet :)