Hello caroleb68

                             We understand that you are having slow speed issue on particular device, for this we need to confirm few basic details to trouble shoot this issue, Your modem current speed plan, to which home network your Cell phone is connected either 2.4 or 5G. Only after confirming this information we can assist you accordingly and you can try basic trouble shooting like restarting or resetting modem then check the speed.

what actual speeds do you get? 

Are you connecting to the 2.4ghz or the 5ghz? (hint, 2.4ghz is a much slower network)