If you work for a company or are part of a union that offers any discount on service with your cell provider; get on that shit. AT&T (for an example I'm most familiar with) will often boot you up to their 'premier' group when this is done (or whatever they call it since I quit) and you get a different customer support group (I was a CS and had to transfer these people out to that group when they called in; whether they liked it or not. I didn't enjoy that transfer; it dinged my stats because it was a transfer).
Call in, ask to speak with 'retentions'. See what the retentions group can do for you if you discuss cancelling your service. You're not obligated to cancel just because you say you're thinking about it and they can't do anything satisfactory to you, you can always just say "I'll think about this and get back to you" and well, never get back to them.
The honest truth - the regular CSRs can't do a whole lot in most cell companies, it's all about that retention team. They have the most options available to them, they'll take the time to analyze your usage and see if you're on a plan that can be reduced to a smaller plan because you overbought your priceplan. They can look for other available discounts or incentives to keep you on with. Outside of them, you'll need a big complaint and a call/letter to the office of the president/vp to even begin to hope for anything else. But beware; I've seen customers get flagged on "corp call" abuse and basically end up banned from the provider. It's rare, but I can remember three specific instances where I received calls from store reps trying to activate a new customer, and it turns out they're denied because of flags on a prior accounts for abusing customer support.
I'm personally banned from AT&T Wireless as a customer for a FCC complaint against a contract change. They let me out of the contract on the promise I would confirm with the FCC that the complaint was settled... and I never came back. I'm okay with that, so it was a perfectly happy arrangement for us.