Mediacom has steadily increased for me, despite no hint of competition. As an ISP upgrades the gear at the headend (CMTS), it just makes sense to offer more and more. Why risk running customers to the competition, even if it’s sketchy? Besides, offering the upgraded bandwidth costs them nothing, they already had to pay for updated hardware, and they’re constantly working on the cable plant (outdoor infrastructure and last-mile stuff).
Caveat: More often than not you have to call and inquire. Last month I went from 250MB down to 1GB, and $10 off for the next year, just by asking about my bill.
It’s really a good idea to call your ISP and phone company once a year or so. No disconnect threats, simply say, “I have some questions about my bill.” If the rep has a deal they can throw you, they just hang it out there. Keeps 'em from getting bitched at. (Been there, been bitched, got the T-shirt.)
While we’re at it, go buy a modem off eBay for $30 and tell your ISP to drop the rental fee. Make sure it’s DOCSIS 3.1 and you’re good to go. Go for used, people are always buying new modems to solve issues they think are modem related, and they almost never are. Oh, and grab a $5 modem at the thrift for an emergency backup! Again, make sure it’s DOCSIS 3.0 or better (it almost certainly will be). Your ISP may not be able to support 2.0 any longer, not sure about that.
Caveat: Due to requiring “5 nines” reliability for 911 access, ISPs usually (always?) require that you use their gear if you have phone service. That’s more a business thing, I doubt many consumers have ISP phones anymore.
SOURCE: Cable internet guy in a past life, in the field and on the phones, Mediacom, Cox and Wide Open West.