I`m trying to find some documentation about how to change ring tone on IP phone 6911, but I'm not able to find some thing clear about it. The only thing I found on data sheet of 6900 series phones:
Multiple ring tones
The phone offers seven user-adjustable ring tones. (6921, 6941, 6945 and 6961).
BUt how is possible you can not modify the ring tone for this model?