If you are one of the owners of a first generation iPhone, and You do not have the visual-voice-mail service I leave you a little trick to make use of this option for your voice messages, whether from the operator you are, such as if you have an iphone for yoigo, vodafone, movistar, entel ... or if you are in Venezuela, Colombia, Mexico, Argentina or Spain.
The first thing you should find out what number you want to use, in this case those of calling the machine that saves your messages, in yoigo it is 633. Then we must write the following code as it appears in the image and give the one called:
* 5005 * 86 *633#
If you are in another country or another operator, you just have to change the number that is in red for the one you prefer.
Now from now on you will have the function activated if you tap where it says Voicemail.
Note: it is not certain that this will work for all carriers in all countries.
Spain: Yoigo (* 5005 * 86 * 633 #) / Vodafone (* 5005 * 86 * 177 #) / Movistar
Venezuela: Movistar (*5005862#)
Colombia: Movistar (* 5005 * 86 ** 123 #)
Argentina: Movistar (* 5005 * 86 * 555 #)
Chile: ENTEL PCS (* 5005 * 86 * # 123 #) Movistar (* 5005 * 86 * 500 #)
Thanks everyone for the tests 