naturally, thick curly hair is really hard to keep straight. the only thing i can think of
is using a relaxer to make it less curly. that might do more damage in the long run though.
i would say instead of going poker straight, just style your hair to a point where its
not so curly. just mildy wavy- if that makes sense.
i know how frustrating it can be. i to have very curly hair and always tried to keep
it straight. after awhile, i just gave up and embraced my natural hair