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I advise you to go (on the phones, if they are Android phones) into the Settings, then the Network Settings, and make sure that one, or the other, of these two is switched Off (as appropriate, depending upon which service you wish to make use of):
- either the WiFi should be Off,
- or the 2G/3G/4G data service should be Off.
When both are On, one can interfere with the other.