It seems you need a HVAC guy to take a look at it. If you want to more prepared (to keep the HVAC guy honest), here are the things you could take a look:
Brand of the HVAC unit/tonnage/refrigent/lbs
What temprature do you set? Is your AC function properly?
How offen do you change the filter (firty coil could cause freezing pipes)? What the temprature of the copper pipe (indoor and outdoor)?
A service call only costs $80 and it does not seem to be a serious peoblem. We do not have to know how to fix the HVAC. We only need to know enough to keep the HVAC guy honest.
BTW, let us know what the problem is if possible. Just curious. Hehe.