Wammu will allow you to gain access to the device in several ways and/or for different purposes. Which task is that you are trying to achieve? Are you sure you marked your phone in the proper mode? For dialing and sending/receiving sms your telephone must be in the "Communications" mode. Please provide this information and/or make sure your phone is in the proper mode. Remember that if your phone is being recognized as a SD, MicroSD reader or Data Connection you may receive an error in Wammu.
By default the majority of the mobile devices are in "data connection mode" which means that: once connected, the device itself is recognized as a micro sd card reader device, thus allowing you to read/write photos, videos, music and so on. For the tasks related to read the contacts, calendar, events and other cellphone related stuff, you must dive in the configuration of your cellphone (usually under "connections") and change its mode to "Communications" or whatever your cellphone allows you to. Depending on the stuff in your cellphone's software is what you will be able to do in Wammu.
Your phone seems not to be fully supported, based on the Wammu support page for Samsung SGH-J700, whose report dates from September 5, 2008. Tested with Gammu 1.15.0
It also seems that no new efforts have been made since that date, so you can only expect the results mentioned in the given site, as follows:
Seems to work reasonably well. Can actually read SIM contacts, no phone contacts as of yet though...
Unfortunately I can't give further details on that phone. New mobile devices are having better support.