Don't call me, I'll call you

Our Sunsynk inverter died and I logged it on the 25th Feb. They said a technician will contact me to set a date and time to come inspect the unit. I had to call them again the next day to find out when I can expect a technician. Eventually, one came and confirmed the unit was dead. He would organise a loan unit and keep me updated. No such update came, I had to call again. Turns out they were waiting for stock. Eventually stock was received and they came to replace it so that my dead unit could be taken for assessment. Cue incorrect loan unit. Back and forth for the correct one. Finally, the loan unit was installed, but not set up correctly, so we were still using grid electricity mostly. We tinkered with the settings again, but it's not the same as it used to be. Also, our pre-paid meter fails comms with the grid constantly so we battle to see our unit balance or load new units. No update as to our dead unit either. I called them to complain and was assured that someone will call me back as "not acceptable practise from us". 24 Hours later and I'm still waiting. 2 Weeks since the logged ticket with no feedback. Aftersales service is pathetic.