You can - poison, traps and bait can be purchased from reputable hardware shops and garden centres. It is very important that you read any instructions carefully before you use any product(s) purchased.
If not used properly and correctly, pesticides or rodenticides can damage your health, the health of any pets you have, and the environment.
If you have a serious infestation, or you feel you cannot deal with the problem yourself, you will need to contact a professional pest control contractor.
However, before you contact a contractor, we would advise that you try and understand where the source of the problem exists. There may be a simple, low cost measure that you can take to prevent its return.
Many contractors will be a member of the British Pest Control Association (BPCA) or the National Pest Technicians Association (NPTA) - both are organisations which seek to promote industry standards of professionalism.