The gta02 is capable of being slightly more open. The difference being that there is OsmocomBB, which is a FLOSS implementation of GSM firmware for Calypso based devices. OsmocomBB still relies on the non-free DSP code from the DSP ROM. The DSP code has a runtime patching mechanism though, so it should eventually be possible to replace it and recent talks at CCC/FOSDEM have shown that it is possible to replace parts of it at least.
Even if there were a "completely" free phone, I would use a landline since there are more issues in the mobile phone space than just the devices themselves.
My point is that completely free systems are not achievable without replacing the current hardware industry with a new one. So one should always say "free enough" or "mostly free" instead of "completely free", at least until we do that.