Mobile network providers must provide telephone number portability for contract customers as well as for prepaid customers. The subscriber is entitled to request porting his telephone number at any time. The subscriber no longer needs to terminate the contract with the previous provider to do so. When porting the telephone number without terminating the contract, the mobile customer is obligated to continue paying the fees for the old and, if applicable, the new contract with a different provider. A new mobile number can be assigned to the old contract.
Whilst in the past it was possible to identify the carrier by the mobile prefix and the charges may be incurred, this is no longer the case due to the mixed range of numbers portability creates. For this reason there are now network queries which provide the carrier the number is assigned to.
For the fixed-line telephone network, the subscriber is only entitled to number portability when terminating the contract with a provider. In addition, the local fixed-line number can only be kept when switching providers within the local telephone network. When changing providers also involves switching the local telephone network, this automatically requires a new number from the new local telephone network. Portability also requires both the old and the new provider having identical customer data. To ensure timely porting, the new provider must submit the request to the releasing provider in due time.