When you buy a service, e.g: get your hair cut or ask a shop to repair something, you have a right to expect certain standards. Anyone who provides a service should:
Do so with reasonable care and skill to a proper standard of workmanship.
The service must be completed within a reasonable time.
Reliable and appropriate materials should be used.
The service must be provided for a reasonable charge, unless a price was agreed in advance, in which case you cannot complain later that the charge was unreasonable.