Yagi -are they necessary?

Recently I went through 2 Yagi antennas and ended up using a Wilson
Truckers Antenna mounted at about 20 feet. The Yagi's I tried did not
work at all. The Wilson gets a decent signal ,3 or 4 bars with my
cingular phone.
If I would not have been cheated by the company in Flushing New York
I bought the antennas from it would have cost less than a $100.00
total.
Be careful who you buy from, it cost me more than $200.00 for an
antenna that the company I bought it from advertises for $89.95 and
they are the highest I found so far. They refused to refund the
difference between the Yagi and the Wilson because they {fixed} my
problem.
I was charged for doing their R&D.