I don’t know what you mean by payment gateway charge but if it’s the extra charge levied by your utility for paying its bill online, I know the charge as “Surcharge”.
I’ve been through the same situation. I always pay bills online only with credit card, never debit card or any other bank account-linked payment method. Until a point few years ago, the utility never charged me anything extra. Then, suddenly, one day, it started levying a 2% Surcharge for all credit card bill payments. I’m quite wary of paying surcharge, so I looked around for an alternative.
I found one finally in HDFC Bank PayZapp app. It’s more frictionless and less prone to failed payment compared to paying directly on my utility’s website. It does not levy any Surcharge for credit card payments. On top of that, it also gives me cashback for paying utility (and other) bills with credit card. Besides, I continue to earn the reward points on my credit card spend as usual. More at HDFC Bank’s PayZapp Ends My Bill Payment Woes.
I also have PayTM as a standby for online utility bill payment in the rare event that I face a problem with PayZapp.