One of the most important things to do when purchasing a mobile phone is to make sure that you can synchronize your contact lists. While the Android OS does a good job of saving your contact books to Google servers, that severely reduces flexibility when purchasing a phone that doesn't run Android. The same thing goes with Windows Mobile Phones and especially those running Apple's iOS.
The best alternative to saving your contact data on a cloud server operated by a large corporation is to use one of these programs that can manage your contacts a synchronize your important contact data with your PC instead. From there, you can even transfer the data to a different brand.
The majority of these software downloads are official applications directly from the manufacturer of your phone. If you have two phones from different manufacturers, you should download each official software programs and explore your options, usually by synchronizing with your Windows contacts (Outlook and Windows Mail).