Really depends on how you want to use it. If you want to only use your answering machine than have the phone company voicemail turned off, if you have U-verse you can do it yourself in the phone portal. If you don't want to use your answering machine at all than turn it off. If you want to use both, like have unanswered call while you're away or to screen calls set your answering machine to answer before the voicemail by either decreasing the number of rings to answer for the answering machine or increasing the rings for the voicemail. The last one will allow most calls to go to your answering machine, but yet still let someone leave a message if you're on the phone and don't want to pick up the second incoming call.
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