Many offices put up with a cleaning company they're unhappy with because switching sounds like hassle. It's usually much simpler than expected, if you handle a few things in the right order.
Check your notice period first
Look at your current contract for the notice period and any renewal terms. Give notice in writing, and keep a copy. If the company has been failing on the service you agreed, note the dates and examples: it strengthens your position.
Don't cancel before you've agreed a start date with the new company, or you'll have a gap.
Plan the handover
Agree a start date, and if possible an overlap of a visit or two. Sort out keys, fobs and alarm codes: ask the old company to return them, and change codes where you can. See how keys and access should work.
Give the new company the specification, any special instructions and a contact for the first week.
Make the first weeks count
Ask for a check-in after the first visit and again after two weeks. Walk the building together or review a photo of the areas that matter most. A good company will welcome this, and it catches small misunderstandings early.
Tell your staff who the new team is, and whom to contact if something's missed.
Switching cleaner is a two-week project, not a six-month worry.
The short answer
Check notice, agree a start date, plan the handover and review after the first visit. Do that and the changeover is barely noticeable.