interest rate

i bought a property trough stardand bank home loan <br> i made a fixed interest rate for 3 yeas and they explain t ome that the payment i making won't change for those years but last month my monthly payment change <br> <br> before month end they said me a massage saying the interest rate is up <br> i call them to find out how is it affecting me beacuse i took a fixed one <br> <br> last month i try to query it again they gave me a reference nuimber and the said their agent will call until today nothing has been done<br> <br> i'm so dissappointed at their poor service