shouldn't exist at all. PERIOD.
Back in the days of AOL, if you didn't have the $25 unlimited plan, they capped your overages at $35. So cap texting overages at $30 or $35, since the unlimited is $20. Cap voice overages at 150% of the unlimited plan. Throttle data by default instead of charging overages, or after a few overage blocks have been used up.
Also, international roaming is an absolute SCAM. There is no reason whatsoever that it should cost 10x or more to use an AT&T phone overseas as it would to use a local SIM. It's one giant internet and network, there is no reason for high roaming charges, or high international charges, since Skype and others have done that for 2.2 cents. If they can do it for that, why can't AT&T do 5 and still make a crapload of money? This is a systemic problem, not a billing problem.
That and cruise ship roaming is insane. The cruise ship operators should eat the cost of the systems, not charge insane overage fees, or insane wifi connection fees. Most of those boats are close enough to land most of the time that they should be able to use masted antennas with ground-based connectivity, not satellite to bring the cost down as well. Connecting a high-speed link over 100 miles or more shouldn't be hard if you've got a 250 foot tower on land, and antennas high up on a large cruise ship, and at that size, you could use tracking directional antennas.