Bad service

I booked in my Fianc?'s Garmin sportswatch in for strap repair,and was quoted R300 for the repair. Sportsmans warehouse did not phone me initially for qoute from Garmin,and I had to go back to the store for information. We accepted the qoute of R300,and left the store. All of this happened before Easter weekend. Today Patricia phoned me,and I was told the watch is finished,and the amoubt payable is R400,the exstra R100 is to cover postage. My question is,why was this not included in the initial qoute,as the qoute given to me was R300. Please clarify this situation for me.