Rock Auto- online auto parts Rock Auto had 1 part number listed for 2 different size engines. They won't admit that their in error and won't pay the return shipping charges. Phoenix, Arizona

I ordered a A/C pump kit for my 97 Monte Carlo Z34 with a 3,4 liter engine.  Rock auto sent me the wrong A/C pump and claimed there was no error in their catalog.  They list same part # for two different engine's 3.1 and 3.4.  Rock auto claims that I didn't read the line at bottom of order form, that says just  v5 and 6 grove.  And that because I didn't describe this, they claim I screwed up.  It doesn't say anything to let customer know that this info has anything to do with placing order.  After checking with AUTO ZONE AND O'REILLY AUTO PARTS THEY SHOW THAT THERE IS TWO DIFFERENT PART NUMBERS AND THAT IT DOESN'T MATTER, SIMPLY BECAUSE THERE ARE TWO DIFFERNENT PART NUMBERS AND THAT HAS NOTHING TO DO WITH V5 OR 6 GROVE. GM made two different A/C PUMPS AND THEY FIT THE MOTORS RESPECTIVELY.  Rock auto agent mgr argued with me for 20 minutes that I was wrong and that they won't pay for returning the wrong parts.  Rock Auto must go a long way training their Agents to not admit that they are wrong at times.  I was always taught that when working for a business that the customer is always right, even if they are wrong.  Well Rock Auto if I had an employee that was as rude as this Idiot I talked to, well he would be looking for a new job. End of story.