If you don't want to be tied to a network, don't buy it from a network! :-)

Pay as you go is just another way for networks to control your phone, don't let them do it.

You can buy 100% of Nokia devices without any kind of network branding as unlocked unbranded SIM-free models, which can be used on any network, or if you prefer you can leave the SIM card out completely and just use them through wi-fi.

You can use SIM-free models with any SIM card in the world.

SIM-free phones are also easier to sell when you've finished with them because they're compatible with literally every buyer's network so you'll get more bids in ebay or wherever.

You can get SIM-free phones (also called unlocked or unbranded phones) from many electronics shops and online places like Amazon, Microanvika etc, and you can also order them directly from your local Nokia website (go to Nokia.com and select your country).

SIM-free phones also get more firmware updates and get them more quickly too as manufacturers always do the unbranded firmware first.

Seriously, if you are annoyed by networks controlling your phone then vote with your wallet and buy a non-network phone. You might think SIM-free are more expensive but they're not, the networks just fool people into thinking they are by hiding the charges on locked phones in various bills and restrictions.