A backed up drain rarely affects just one person. The only bathroom is down, or the kitchen can't run, or the whole household is waiting on it. That makes the common mistake more expensive here. Drain equipment comes in tiers, and the tier that shows up decides whether the visit gets anything done. A short snake reaching for a clog it can't get to wastes everyone's time.
Here the sorting happens on the phone. You'll be asked which drain, how often, who to contact for access, and what's been tried. Those answers help decide who gets sent and what equipment they bring. A standard clog gets the standard machine, a deep blockage in an older line gets the longer cable, and a clog that keeps coming back gets the camera, because seeing the problem beats guessing at it.
You hear what was found, what was done, and what to watch for, all in plain English.