Money paid for service not rendered.

What a dreadful experience we had when we took our Isuzu in for it's annual service on the 28th of December 2022. When we collected our vehicle they informed us that we would need to bring our vehicle back because they did not have the grease required for the wheel bearings. First reaction shock that they do not have a competent buyer & then annoyed that they expected us to bring our vehicle back due to their incompetence. We paid the full invoice including the work not done. A week went by & we tried calling & always ended up leaving messages with the receptionist, no one ever called back. We then went to their premises on the 7th of January expressed our dissatisfaction & requested a refund for work not done. On the 9th of January we were told our refund request was sent to head office & to expect our refund up to 7 days from I assume the 9th of January. It is the 27th of January & no sign of the refund & worse no replies to my e-mails from Shanique who originally told me the refund would be paid up to 7 days & a reply from Gregory the service manager saying when he hears back from head office he will let me know.