Wireless phones as in cordless phones? Wireless N is dual band 2.4ghz and 5ghz. So the interference from cordless phones would depend on the frequency of the phone and the frequency your wireless clients are connecting at. Either way if you are referring to cordless phones you appear to have a rather noisy one as related to the carrier frequency of the channel your router is one:)
The default setting for the channel on the router is AUTO, the channel is set on router bootup so if you are not on the phone at the time the router will pick the cleanest channel, which may be the channel your phone system uses. Then when your phone is in use, interference happens.
One solution is to choose the best channel manually by trial and error (keep in mind that once you appear to have the best channel, someone will use the microwave and you will start testing over again
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to choose the best channel not affected by the cordless phone or microwave.
Another solution is to switch to a DECT coordless phone which if memory serves uses a carrier frequency below the 2.4 ghz band