Question about Sony Xperia Z5 Premium

Contract extension, like the name implies, extends your existing contract. This means you must already posses a valid contract with one of the service providers. Therefore whatever contract you currently have and when you select the option Contract extrension, your contract will be extended by the selected period. For example, if you are still bound by your contract for 10 months till it would run out, selecting a 12 month extension, would make it 22 months. Thats the downside, you are bound by contract and you have to pay the monthly fee till your contract runs out. But you might get the smartphone for a good deal.