Terrible after sale service

I traded in my Chery Tiggo 7 for 2 cars - 1 x new, 1 x "demo". Whilst deal was being processed the Sales Manager Maggs called literally daily - I gave them my budget (which was slightly exceeded) however I excepted. I am livid with the terrible after sale service. I have taken delivery of both cars....the "demo" had to be parked as insurance wouldn't cove it without a disk. After delivery no communication/update or feedback. I went to the dealership & all I got was pathetic "sorry ma;am"....i was promised by MAGGS that there will be no debits in February but that was a lie. I called to speak to finance manager & he tells me he doesn't know how long the process will take for MAGGS to sort out my issue. I called back again but to no avail to escalate my issue. The finance manager said the installment debited would be refunded but......i feel i can return the cars & take my car back & just cancel.