The online ported number search page will tell

Switching to another mobile service provider is not too complicated today even if you want to keep your old phone number. Administration of number porting is simple: you only need to inform the provider you plan to switch to and they will arrange the rest in as little as 2 days.

However, ever since number portability became a reality, area codes can no longer be used to determine the provider of a given telephone number. Instead, all it takes is a few clicks on an online ported number search page operated by the NMHH. The website is very popular with over 100,000 user searches since its launch in February 2015.

The service is available at http://krapub.nmhh.hu/