Uber dishonest

Quoted one price, then get charge a different price when trip completed. This has been happening frequently lately. I've been riding Uber to work every morning for the last 4 weeks, same address. Some days it's fine, other days they charge me. additional fees. I then complain and get refunded the difference. Happened again today, now they are refusing to refund me the difference between price first quoted and the extra fees.