As a solo developer, I decided to offer phone support
I did it for 10 years, but more recently have moved away from phone support as much as possible (or delegated to others to do).The main reason - I am a solo developer.  And the brain mode for 'developer' is VERY different from the brain mode for 'support agent'.It was basically impossible for me to get into 'flow' state during a normal working day.  Even one phone call during the day took me away from my creative, programming mindset and into an empathetic, listening mindset.  And the transition between the two were very different.  It's like asking a racing driver to knit a scarf each time he came into the pits, before he could go out on the track to drive at high speed again.It also made it hard to plan blocks of work.  Most times it was OK, but there were days where I would plan to do about 5 or 6 bug fixes, but I would get a slew of phone calls that meant I got 0 programming done that day, and would have to move other plans.I actually enjoyed support, but in the end I had to decide which of the two parts of the job was moving the business ahead more than the other, and pure development work won out.