Determination of the Autoridade Nacional de Comunicações (ANACOM)
It is now possible to maintain the same telephone number when you change operators. This option is available for both mobile and fixed numbers and is known as "portability".
Portability is especially useful when you intend to opt for services or prices offered by other operators, but for various reasons wish to maintain your existing telephone number.
In order to port a number, i.e. to transfer it to another operator, you simply need to contact the new operator who will provide you with all the necessary information, including whether or not there will be a charge for transferring your number.
As soon as a number of a fixed or mobile telephone is ported, all the figures will be transferred to the new operator, including dialling codes. Remember that the number remains unchanged, but will be "connected" to this new operator chosen by the subscriber .
For this reason, when you dial a ported number it is probable that you will be dialling a network other than that indicated by the number itself. If the network is different, the connection charge is also likely to be different, unless the tariff plan contracted with the operator establishes that the price of calls does not vary in function of the mobile or fixed network for which one dials.
As a result, those operators with a tariff plan implying a higher cost for calls to ported numbers, should offer a telephone information service with information on the price that a user will be charged for a specific connection. The access number to this information service should be identified in each customer's normal bill.
This measure was decided by the Autoridade Nacional de Comunicações (Anacom) - the authority responsible for regulating the telecommunications and postal markets. ANACOM is able to provide further information on this matter: via the Internet Online Services desk at https://www.anacom.pt/render.jsp?categoryId=2, e-mail address, 
info@anacom.pt, freephone number 800206665, and to attend enquiries in person in any of the public attendance services distributed across the country.
