ok my w800i is not turning on i tried changing to a new battery and all but i dont want to loose the numbers would i be able to maybe cuy a cheap one on ebay and transfer the phone memery ito the other one. it was playing up abit b4 it said sim falier etc b4 but then was back to normal after turned of and then back on
Sounds like software problem, try installing SEUS update software from Sony Ericsson, follow the instructions & update the firmware to the latest (for free) and see if that sorts it.
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Try fixfault.com to fix mobile phones.