Hello-
There are some things that need to be checked:
Is there a good, clear "line of sight?" That is, are there no trees or branches near the dish itself? As trees grow and bloom, and as the wind blows the branches, it can play havoc with reception. Bad weather can disrupt reception also.
If the issue is reception, then it is probably most certainly an issue with the dish and mast itself. Possibly it is mounted in an unfavorable or unstable spot. The mast may not have been checked to assure it is level both vertically and horizontially, and/or the skew and elevation settings on the polar plate may not be correct....or the bolts are not being tightened good.
The guys coming out, are they Dishnet certified, or are they just someone hired by the local retailer with no real training?
You might also check to see it it's grounded. That has nothing to do with reception, but any installer who knows what he's doing will have grounded it.