Traveler Alert: Roaming Charges for Unanswered Calls

By Jonathan Spira on 1 September 2009
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Business travelers traveling overseas with a mobile phone that supports international roaming should be aware as to how some calls are billed.trombone Many people assume, incorrectly, that if they allow a call to ring and then go to voicemail, they won’t be charged.  In actuality, such inaction might result in a billed call due to a phenomenon known as “tromboning,” a process where the call goes through an extra circuit to get to its destination (imagine a trombone player pulling out the slide, thereby creating an extended route from mouthpiece to the end).

Because AT&T and T-Mobile have GSM networks, standard in most countries outside the U.S., more of their customers are likely to roam internationally.  Sprint and Verizon Wireless have CDMA networks and their customers’ mobiles won’t work overseas with the exception of specific dual-mode phones that support CDMA domestically and GSM out of the country.

Verizon Wireless is the only mobile operator that does not charge for any calls that ring and then go to voicemail.  Sprint does not charge its CDMA customers in such cases but does charge Nextel customers with iDEN-based phones.

Here’s how AT&T and T-Mobile explain it on their Web sites:


“Calls that you do not answer that are routed to the AT&T voicemail system will be charged as an international roaming incoming call to your device.”


“Unless you switch your device off or activate Unconditional Call Forwarding on your device, you will be billed for calls delivered to your voice mail box while you are roaming internationally.”

It’s even possible for tromboning to occur if you leave your mobile phone off most of the time because it will register with the foreign network and that could still cause calls to be forwarded to your overseas location and back – resulting in a hefty bill when you arrive home.  In addition, depending on the policy of the foreign operator, the bill might be for the call to your location and back to your home network.


Mobile Operator




Sprint – Nextel (iDEN/GSM )

Sprint (CDMA/GSM)

T-Mobile (GSM)

Verizon Wireless (CDMA/GSM)

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