Depends on the make of phone and if it's a fixed land line or mobile. If a fixed land line ask your provider for help/if a mobile again phone and ask the provider. OR: put the make of phone in to a search engine to try to track down an Online manual to down load/forum to post question/email for help/etc.
May
September 2011
Automatic Answer
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howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix corded phones.