If they are too wide, you can trim the ends. As I told another member who asked the same question before, without opening up the strap and trimming the ends, there is not much you can do. One option is to get a pot of boiling water and quickly dip the end of the strap into the water. It will shrink the leather significantly, which might or might not have a good result. It also hardens the leather a bit which may or may not be desirable.
Many strap makers do not take the time to thin the leather that attaches to the case. It takes more skill and time to do but will guarantee a better fit. This was apparently not done for your strap if it is too thick and not too wide. One possibililty is to remake the strap by unstitching, trimming the end and restitching, but it takes quite a bit of work and there is no guarantee it will look the same as what you have. If you post a picture, I can help more......