Text donations

I've been tasked with lookingat text donating.

I've got some good links:
http://www.ctt.org/products__services/sms_txt_giving/default.asp

http://www.smstextgiving.com/

http://www.justgiving.com/design/93/sms/default.asp

However, not many charities (that I can find) seem to offer SMS donations.

Is there a reason for this?

If your charity does offer SMS donations, then could you let me know please?

Thanks,

David