why WoW internet service never bill correctly?

we received wow adv. showing if before Mar 31,,2021  became client can get internet 100 from $39.99 down to $29.99 included autopay and paperless (ps enroll autopay get $5 credit and paperless $2 credit).

we did switch to Wow and turned out Mar $39.99, Apr-Jun $34.99 we kept disputed and each on line chat worker we got different answear such as $29.99+$5 tax=$34.99, 1st month Mar didn't count as autopay so $34.99+$5(autopay)=$39.99. they don't admit any wrong calculated.

finally a lady agreed it should not be charged $34.99. so July $34.99-$5 -$35(i have no idea, could be refund $10(Mar)+refund $5x3(Apr-Jun)+rewards $10(for company mistakes)) -tax $0.41(i have no idea, could be overcharge $25(mar-jun reduced tax?)=-$5.42. ie i didn't need to pay july and still have $5.42 credit.

ps in May i did switch another credit card then the system and/or other online chat workers didn't treat Mar-May as autopay(i would say because the system didn't keep all information so assumed autopay began when new credit card entered, finally the lady agreed switch to another credit card before and after still should count autopay.

in Aug $34.99-$5-tax $0.41(i'm sure it is the difference of $34.99 tax-$29.99 tax)=$29.58 ie monthly fee is $29.58 not $29.99. so i was charged $29.58-$5.42=$24.16

if it is correctly then Sep should be $29.58 but online showing $44.99 -$5-tax $0.41=$39.48 so i can't but disputed again.

Jxx: ...You were just having no discounts before, but for now, I'll add it... Your new monthly rate is now at $29.58 starting on the next billing cycle.
Your current bill is prorated to $30.91.Meaning, for this month, just pay $30.91 and on the next billing cycle, your new bill will be $29.58.

(I have no idea the autopay date on 9/25 why should i pay $30.91 not $29.58, having no discounts before? i got refund on July because their system or their staff didn't do job right) so i request Jxx to review my July statement.

Jxx:For the autopay, your account was enrolled last May 22nd. The $5 autopay discount will be available starting on June.

you had no discounts before and it was not an obligation. I am just giving you a discount now since the account is eligible....in the end want me

ps in their online statement i found out what's wrong. the system used $44.99 -$10(6 mm promotion) =$34.99 not adv. showing $39.99-$10(12mm promotion)=$29.99

it did correction on Apr as: $34.99+$5-$10=$29.99(ps i don't understand why not $34.99-$5) but Mar didn't correct it, this is why became $34.99(Apr-Jun) and can see their online chat workers are random say say. until the lady refund in Jul. but today Jxx won't review July statement insist his opinions won't correct sep. wrong charge($30.91 in stead of $29.58). he can't see their system bug.

when Mar we swiched and paied by phone was charged correctly, but system statement didn't correct. so it never corrected and their workers never found the bug. tonight i almost wanted to cancel autopay because charged wrong amount forever and every time spent lots time to dispute their online chat workers. we were Wow client in May,2015 to Jun,2017 then switched to xfinity because bill statements always wrong, tired of disputed. we switched back to Wow because when neighbor snow shower worker hit the outdoor internet boxes in Jan? caused internet poor connection and called to replace box but never showed up until july?.