Ok. The "PHONE" problem is that the radio thinks that a call is coming in. This is because:
1) the "tel mute" pin on the rear of the unit is being pulled to ground.
2) the unit is mis-reading the fault.
to determine which it is, disconnect the accessory connector from the rear of the unit. There are 3 multi-plugs on the back, one for power; one for speakers; one for accessories. it's the shorter, wider on in between the others. There may also be a green CD changer connector and there is the antenna.
If the fault is still present, then I'm afraid that it is a faulty radio. try cleaning the connector PCB with IPA or similar.
If the fault disappears, then it is most likely that a mobile phone kit has been installed and is causing the problem. usually, there will be a wire to the accessory connector that has been added. eg. not in the vehicle loom. This is usually yellow. simply remove / cut this wire. This should clear the fault.
Hope this helps.
As for the "VOLUME/SPEEDO" problem - these units have a feature called "AVC" - Automatic Volume control. The unit receives a signal from the PCM which tell it how fast the vehicle is travelling. the unit then adjusts the volume to compensate for road/engine/wind noise.
It is (in my opinion0 likely that your VSS - Vehicle Speed Sensor is faulty. I would recommend replacing this, as the PCM relies on this signal to manage the engine fuelling/ignition properly. Also, if you have a fuel/trip computer fitted, this will be giving false readings.
I hope I have added some useful info here.
PipeManPeep, July 2013