Cannot Access Sip Phone via Ftp?

I have a swissvoice ip10s and need to update the firmware. I can access the phone via a web bwowser by imputting the ip address of the phone, my problem is I am trying using FlashFXP ftp client to access the phone, I am using the same ip address user name & password but not able to connect to the phone, I am using the dedault port 21. Can any one please help?
The phone ip can be pinged, also used smartFTP client the same problem!