If you run across a number with only five digits, it's a remnant of the old system that was changed in 1999. Because telephone communications are difficult, many people in the travel business have mobile phones.
Calling within Tanzania: The "0" in the regional code is used only for calls placed from other areas within the country.
Calling Tanzania from abroad: To call from abroad, dial the international access number 00, then the country code 255, then the area code, (e.g., 22 for Dar es Salaam), and then the telephone number, which should have six or seven digits.
Mobile Phones: Vodacom, Airtel Tanzania, and Zantel are the main service providers in Tanzania. The best option is to bring your own phone (if it's not locked to a particular network) or rent a phone and buy a SIM card on arrival. The starter packs for pay-as-you-go cell phones are very reasonable. You’ll have to buy credit for your phone, but this is easily done at shops or roadside vendors.
Airtel Tanzania. www.africa.airtel.com.
Vodacom. 082/111; www.vodacom.co.za.