XFINITY web site makes if almost impossible to pay my monthly internet bill on time

XFINITY web site seems to work for most everything except for paying my bill.   Almost every month when I try to pay my bill, their billing portion of their web site doesn't work and just generates a "Sorry.  This isn't working right now" error on the web page,   Then I end up paying my bill late and get charged an additional $10 late fee.    Clearly, this is a pretty convenient way for XFINITY to make some extra $$$ when the billing portion of their web site is constantly malfunctioning.  So starting this month, I'm no longer going to pay their late fee.  If I pay my bill late because their web site "isn't working right now", then they simply get paid late.    I'm also not signing up for automatic payments.  XFINITY can cancel my account if they wish because of my unwillingness to pay their late fees but, I'm not getting scammed by them any more.   There are plenty of other excellent internet providers in my area.