Figuring out the best cellphone plan has always been a challenge for several reasons: You can’t believe everything the carriers tell you, the plans are constantly changing, and there are always exceptions to every plan. Additionally, the best plan for you depends on your needs, your location, whether you are a single user or part of a family plan.

For example, T-Mobile offers unlimited voice plans, but then charges by the minute for calls to some numbers, such as conference call services. All carriers offer unlimited data, but that may exclude using your phone as a hotspot, and some of that data may be very slow.

You’re supposed to read the small print to figure out these exceptions, yet it’s nearly impossible to do. You learn only when a surprise charge appears on your bill.

Usually, the best plans are for new customers, while long-term loyal customers are taken for granted. When rates go down or new plans are introduced, none of the carriers will tell you – you’re on your own to learn about them and take action. Wouldn’t it be nice if a carrier just guaranteed you the best rates available?

The best way to fight back is to be aggressive with your carrier and be willing to switch if necessary.  No longer are you tied to long-term calling plans, and many phones will work on multiple carriers. Call your carrier every quarter or whenever you read about a new plan, and tell them you need to reduce your costs or you will switch. More often than not, they’ll find a way to either get you on a new plan or reduce some of your costs. I just did this with Verizon and they reduced my connected iPad charge from $10 to $5/month.

With all the new plans being announced over the past few months, Tom’s Guide compared the latest offerings and came up with the following recommendations:

I’ve made trips to Asia and Europe and have been impressed at how well T-Mobile works for data everywhere I’ve gone. The other carriers continue to alienate travelers by charging huge data fees and voice calls at about $2 per minute or require you buy a daily pass for reducing your costs just for that day.

But with even these unlimited data plans, read the small print. No one gives you unlimited high-speed data, otherwise, you could cancel your Internet service from your cable company and just use your phone as a hot spot. They all throttle back the speed after some level of use, and some have restrictions on using your phone as a hot spot.

Generally, you can save the most money if you can put several phones on one account. I have a Verizon family plan that includes five family members with five phones and a tablet splitting 16GB data for about $250/mo and allows tethering. That averages about $50 per phone. Verizon and others now do a better job of warning you about data usage and offer an option to slow your data speed when you exceed your monthly limit, rather than charge ridiculous overage fees. But you need to elect that free feature.

If your family is small, combine your plan with another family to put four or more phones on one account. The benefit comes from the data dropping in cost the more you buy and then splitting it among additional users.

I also have a T-Mobile phone I use for international travel, and it costs $60 per month. Its free international data and low-cost international calling more than pays for itself compared to the data charges I used to pay from Verizon on a single trip.

The bottom line is you should pay no more than $50 per member for a family plan inclusive of all costs and $5 to $10 more for an individual account, each with sufficient data. If you’re paying more, you’re paying too much.

Thankfully, online customer service has improved, and I have had good success when I’ve called T-Mobile and Verizon. Often the customer service agent will aggressively look at ways to reduce your bill, including analyzing you historical patterns.