When hiring cleaning companies, it's crucial to clarify exactly what tasks are to be performed and the condition of the premises from the outset. Otherwise, differing expectations can quickly lead to dissatisfaction. I've had good experiences with conducting a site visit beforehand and documenting the scope of work in writing.
It's also worth asking if the same people always come and how they handle any necessary revisions. Price isn't the only factor; reliability and clean workmanship are equally important. A clear agreement is essential.