- People mis-dial, a lot
- Equipment mis-dials
- Connections go wrong some times
- Links in the phone network can be congested
- Sometimes you get one-way audio (rare)
- Sometimes you get audio breakup (mobiles usually)
- Sometimes calls drop for no apparent reason
- Sometimes people answer the phone and drop it and so cut you off instantly
- Sometimes phone handsets are faulty, especially if ever you spilt coffee on them
- Headsets can have the mic pointing the wrong way so you can't hear people
Now, normally, when shit happens, people happly ignore it, try again, maybe puzzled by it if it is unusual, but that is it.
But if ever you "update the phone system" in any way shape or form, then every minor quirk is reported as a problem. We used to install phone systems and this was a classic feature of the initial support - explaining that "Yes, they called from a mobile and went through a tunnel so the call dropping is not a surprise. No, it is not a fault in the new phone system"...
Thankfully our customers are being relatively sane on this, phew. But it really is amazing what you can find if you actually go looking for problems!
It is also quite hard when there really is an intermittent problem to tell if it is real or not.
All good fun.
P.S. The classic one is "If I call a land line, and they hang up, the call stays connected". People are so used to mobile and SIP now they expect that when one end hangs up the call ends. People forget that land-lines don't actually do that! You can hang up, walk to another extension in the house, and pick up the call. It can take minutes to actually clear. Land-lines have been like this pretty much forever and it is not a fault :-)