I went to the same company-owned store I bought my Sanyo 7400 from a
couple of months ago, starting a new two-year contract.
The earpiece got progressively worse in sound-quality, as for me to
hardly understand the conversation.
I asked for a replacement or repair.  After they looked at it, they
said no, as there was "nothing wrong with the phone."  There sure was,
with the sound quality absolutely terrible.  While waiting for my
phone, I tested other Sanyo phones in the store.  Many sounded bad too,
my mine sounded the worst.
The phone in its present condition is worthless to me.  So I call up
Sprint directly.  They said they couldn't help me.  So I said fine,
just cancel the account, refund the purchase price for my phone after
the $150 rebate they sent me (I offered to send the phone back to
them), and don't charge me a $150 early termination fee, since they're
not honoring their warranty or conditions to my contract, since I have
a phone I can't call from and can't do a thing with.  They refused,
even after talking to two supervisors.  I've been a customer of them
for four years, but it took four years for me to suddenly figure out
what an unethical company Sprint is.  They're awful.  Avoid them at all
costs!