Do your mobile phones support 5 GHz? Do they connect if CPE's channel width is limited to 20 MHz (some client devices have problems with 40 MHz channel width)? Are you in the range of the CPE's WiFi signal (it has only a 45° beamwidth)? Do you have turned off the CPE's MAXtream? Are your mobile phones in free line of sight? If so, what distance is between mobile phones and the CPE? Do you use the correct WPA2 encryption mode so the CPE can use 802.11n (should be AES if WPA2 is used at all)?

There would be much more information required to be able to give any advice of how to resolve this.