Very disappointed

We got a Daikin heat source pump fitted in our property over a year and a half ago.
We are paying monthly payments to pay for the system as was explained at the time of sale. We were also advised that over a 7 year payback period the system would pay for its self due to the ofgem payments we would get back every 3 months.. May we just say looks like this will NOT happen.
After calling the company every day for nearly a month.. 9 months after the system was fitted they reluctantly send the paperwork. Can remember a few of the advisors names. They were just passing us from pillar to post.. BUT we ever gave up on getting paperwork sent out. We did not get any apology from the company at all.. Feel we were Mis sold an item and due to not having relevant paperwork never got payments we should have got from Ofgem.
My math states 15000 loan over 7 years with an ofgem payment of 50 every three months is definitely not a system paying for its self?