Will not give us what we paid for

We bought a big g package from them with 12 panels an inverter and two lithium batteries,they sent their guy Christiaan to install it,when the guy arrived he said the new inverter was still on its way and he will install another till the new one comes,months later my mom who is in her 70’s asked him about it and his reply was if it’s working why change it,my mom is old and did nothing but a while later we started having issues so he came back and sold here another inverter and battery so now we have two inverters and three batteries,a while after that the inverter broke down and he came and took it in and got it repaired instead of replacing with he new one we paid for,my mother forgot about it that time,it broke down again and this time she remembered it and said she wants her new one that she paid for and she will call full circle about it,they say he doesn’t work for them anymore and he says he works for himself,now cause of this faulty inverter one of the batteries does not work so they both say they will fix the issue and replace the inverter,they didn not,they repaired the same one and only charged the battery and it still doesn’t work right and effects the entire system,they ignored all calls from my mother,I will have to get another company to have a look at what they have done and am now seriously thinking of taking them and their guy to court over this,they refuse to give us the inverter we paid for and leave us with a second hand one and I’m sure that the third battery we got was also second hand and at the end of its life