One of the most crucial steps in successfully planning a trip to a foreign country may be making sure that your communications setup does not falter or end up costing you a fortune in calling, texting and/or data fees. That means you may have to adjust your smartphone plan with your provider at least temporarily to make sure that you get good reception and avoid being charged an arm and a leg for using your phone while away.

Providers usually are willing to change subscribers’ plans to accommodate foreign travel and then change them back again without hassle, but be sure to allow enough time for the change to take place so that it coincides with your travel dates—ask your provider when you should order the change to allow for that timing.

If you have an “unlocked” phone and are planning an international trip, this could be a smart time to look into switching to a plan from a different provider.

Here are the best international roaming options* from each major US cell-phone carrier in declining order of attractiveness plus the two best deals offered by smaller carriers…

The Big Carriers

T-Mobile One is a plan that includes unlimited calls, texts and five gigabytes (GB) of data per month at fast 4G speeds in Canada and Mexico at no additional cost. In more than 210 other countries, unlimited texts and slower data speeds (at 128 kbps) are included at no additional charge. Calls typically cost 25 cents per minute (more in some countries).

Sprint Global Roaming, which is included automatically with many of the carrier’s unlimited plans, provides unlimited texts and 2G data at no additional cost in 165 countries. Call costs vary by country but are 20 cents per minute in many popular travel destinations.

AT&T Roam North America, which is included or can be added to many AT&T unlimited plans at no additional cost, provides unlimited calling, texting and 2G data in Canada and Mexico. Outside North America, customers can make unlimited calls to the US and within the foreign country and send and receive unlimited texts with a $10/day International Day Pass. They also can use their plan’s high-speed data ­allotment in more than 100 countries with the International Day Pass.

Verizon Go Unlimited, Beyond Unlimited and Above Unlimited plans allow customers to use their plans’ calling, texting and data allotment in Canada and Mexico at no additional charge. With many other Verizon plans, customers can get this benefit by paying $5 per day for TravelPass. Verizon charges $10 per day for TravelPass in most other countries. (The Above Unlimited plan includes five daily TravelPasses per month at no additional charge.)

Smaller Carriers

These smaller players offer notable foreign roaming deals as well…

MetroPCS customers who have base plans costing $40 or more per month can pay $5 per month extra for “Canada Unlimited” or “Mexico Unlimited” to get unlimited calling and texting plus up to 5 GB of 4G-speed data in those countries (slower speeds when 4G is not available). Elsewhere, the MetroPCS World Calling program provides up to 200 minutes of calling, 200 texts and 200 MB of data in more than 75 countries for an additional $10 per month. (4G speeds are not ­guaranteed—slower speeds might apply in some covered countries.)

Project Fi customers pay $10 per GB for data in more than 170 countries—the same rate they pay in the US. There’s no additional charge for texts, while calls made abroad cost 20 cents per minute. Turn on “Service outside the US” and “calls to non-US numbers” in a Project Fi online account to enable this. ­Project Fi features a very limited number of phone-model options, however…and while its $10-per-GB data rate is appealing for international roaming, lower data rates are available from many other carriers within the US, so this might not be the most cost-effective plan overall for people who use lots of data.

The SIM Card Alternative

If you have an unlocked phone, instead of changing your smartphone plan, you could buy a local SIM card for the country you are visiting and install that in your phone. Your phone will have a local phone number while you use the foreign SIM card, but you still can use apps such as Facebook Messenger and Skype to call back to the US affordably. Local SIM card prices vary, but in many countries, it’s possible to obtain cards that offer a reasonable amount of data and prepaid calling minutes for $20 to $40. You might need a different SIM card for each country you visit, so this option makes less sense for multination tours. Mobile-phone stores and electronics stores offer SIM cards and might be able to install them for you at no additional charge (the cards are sold through vending machines, newsstands and other locations in some touristy areas, too).

If you don’t have an unlocked phone, another option is to purchase a cheap phone and prepaid plan in the country you visit—though that would mean you don’t have a modern, versatile smartphone—or rent a local phone through a company such as TravelCell.com, though this can be pricey.

*International roaming rates, which may change, typically apply to calls within a foreign country and from that country back to the US, but higher rates might apply to calls from one foreign country to another.