W/C Batteries rip off?

I don’t know if this is the norm or not but something sure doesn’t seem right with this picture. My original W/C batteries lasted 14 mo., replacements lasted 18 mo. My last ones went out at 6 mo. ( I do not udse my W/C excessively). I called my dealer 90 miles away and they would not get here for 3 weeks. In the meantime I checked on line and found out that particular battery has a 1 year over-the-counter free exchange and a percentage of use for 18 months after. When I informed the dealer of this I was asked (in an acusing tone) “Who told you that?” and she insisted no it’s 6 months. My son and I talked to that battery brand dealer here in town and was assured I had the right information, nice lady even called the home office to double check for me. Out of customer courtesy she asked that my son bring the batteries in and if found defective they would replace them free of charge even though they were not bought there. He did and installed them (free replacement) for me. They sell the batteries for $120. each. I have Medicare and a supplement insurance but Medicare will only cover the batteries once a year which they did 6 months ago. They were billed $540 which Medicare cut down to $279. Would I have had to pay the inflated price? I don’t understand why the W/C dealer does not honor the battery warranty. Except that he would then have been able to turn my old batteries in for new ones, profiting by $240., while at the same time charging me for replacements. Thank God I have a son who can help me with this kind of thing. What about the person who doesn’t?