Sorry to hear their response didn't help yet. Please let them know and they will certainly continue to assist you.
Note that AmpliTube 5 CS does not include a large part of the new AmpliTube 5 technology, a huge part being the VIR™ technology which is a massive improvement in the cabinets with 600+ impulse responses per speaker so that is one of the main reasons people do upgrade. The charts on the
AmpliTube 5 page should indicate any of these difference for reference.
AmpliTube 5 CS definitely does not include the mixer. This is indicated in the comparison chart on the
AmpliTube 5 page, I just double-checked. You can click the "Compare Versions" button on that page to see the full comparison chart.
If there was an error in your access, the support team can take a look, but going forward the information above is correct and what you would be entitled to with AmpliTube 5 CS. To get the mixer and other features you can check that comparison chart and choose one of those versions noting what I post immediately below that you have not missed out on the introductory pricing.
The introductory pricing on AmpliTube 5 has not changed. You are still OK there.