Incorrect components sold and refusal to exchange or take it back

I was sold a backup power supply with a battery for my intercom which was the wrong voltage and could not be connected to the system. I took it back today and was informed by the manager that they have a policy not to accept any electrical equipment. They did not care about me as a customer even though they made the mistake in selling me the incorrect equipment. Please do not support them as they clearly operate with ******** intent. Do not buy anything electrical from them as you will be sold the wrong components and you will not be able to take it back. I will certainly never buy from them again.