It sounds like the approach to solving your problem so far hasn't been very systematic or "evidence based" – at least the list of parts replaces suggests that the people working on it have been using a "shotgun" approaching, replacing parts in hopes that one (or more) of them will solve the problem.
Start off by doing basic checks:
Is there hot water available? It could be that your engine is not coming up to operating temperature. Check the temperature gauge if you have one and also the hoses going to the radiator. After 10 or 15 minutes of operation the hoses should be very noticeably hot.
Is there power to the heater controls? Does the fan run? Check all of the fuses related to the heating system – especially if the fan or the heater controls appear to be not working.
Do the heater controls seem to be working (can you hear the blend doors move when you change the controls, does the fan run, do the heater hoses change temperature when you adjust the temperature control)? Learning which controls work (and maybe which don't) will help you to isolate the problem areas.
Is hot water moving through the heater core? Check to see if the hoses going to the heater core are getting hot. They will be cooler than the other cooling system hoses if no water is flowing through them. If the hoses do not seem hot, there are two likely possibilities: one is that the cooling system has air trapped in it that is preventing hot water from getting to the heater core, and the other is that something, perhaps a kinked hose under the dash, is restricting water flow through the heater core. If you squeeze the hoses as if to close them off while the heater is "on" you may be able to feel water moving through the hose.
Check for obstructions to the air flow through the heater – one of the few things in the heating system that I don't see on your list is the cabin air filter, so confirm that it is not plugged. Also confirm that when the fan runs you get air movement through the vents.
Finally, at this point it would be wise to assume nothing. So much has been done (and seemingly without a methodical approach) that it is possible that there are compounding errors or problems. Run through the list in order eliminating possible problems. Most of them are checks that you could probably make yourself, then when you isolate a potential problem area you could either ask another question based on your findings or take that information to a mechanic. When the mechanic does work, ask that s/he explain the thinking and evidence that went into the work.
