How can i lock key paid for sony w700i? - Sony Ericsson W700i Cellular Phone

SOURCE: UNLOCK CODE OF SONY ERICSSION W700i.

first of all let us know weather your phone is locked or sim if it is phone through your IME no we can try to do it, but let us know which is locked

SOURCE: security code lock

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SOURCE: how to lock my phone sony ericsson w700i

You'll need to purchase an unlock code.
You will probably find a number of companies via google a I have used a couple, which I'm not sure I'm allowed to post here so I recommend you visit Unlock-Zone.com, which is nearly perfect and they were recommended highly in the cell phone forums.
Click the unlock your phone and select the mobile phone, current service provider to get the available unlocking service which ranges from $5 to about $25, depending on the model of phone you have.