MKEM has poor service

It sounds like you had a frustrating experience at the dispensary. Here's a possible rewording that maintains your tone:

"I recently purchased sensors for over R1000, but when I tried to exchange them just 5 minutes later on the same day, the staff refused. The staff member on duty seemed unhelpful and unfriendly. It's disappointing that I had to take time to resolve the issue myself when they had the necessary stock. The store's cleanliness and parking area also left a lot to be desired. Given this experience, I won't be returning and plan to file a complaint with the relevant authorities."

"The premises are poorly maintained, giving off a run-down appearance. It's disappointing, especially considering the financial transactions that take place there."