Bosch Boiler and Thermostat Installation Woes

I recently purchased a Bosch boiler as well as a Bosch wired room thermostat. However, during the boiler installation, I was informed that the thermostat could not be installed because a connecting cable was missing. They recommended that I hire a professional to install the wiring and that even then, I would be charged a service fee for the thermostat installation. Now I'm left wondering: Is it Bosch's fault that they sold a wired room thermostat without the necessary cable, forcing me to rely on an electrician? Or is it the fault of the service for failing to provide a solution during the initial setup and then demanding a service fee on a subsequent visit? Finally, the customer is caught in the middle, concerned about voiding the warranty while being abandoned by Bosch and the service. I demand that my thermostat be installed quickly and without charge; otherwise, I will be forced to take legal action against this unfair system that consumers are forced to accept.