Chev Aveo audio system

I brought a Chev Aveo 1.5 LT from Gauteng to Bloemfontein, Free State, where it will now stay permanently. However, the radio does not give proper station reception in Bloemfontein. When scanning, it skips all even frequencies and display only uneven frequencies. I believe this to be the reason for poor reception. In the owner's manual, reference is made to an Area Frequency (AF code). Could this be the problem and can it be changed? If so, any suggestions how to do it and where to find the correct AF code for my area?