Hi!! Unfortunately there is no "permanent" fix to get your hair straight (trust me, I've tried). At the hairdresser they can perform a chemical straighten, which is sort of like a perm in reverse. I think there are also similar, but more updated techniques. But of course, it's like having a colour in your hair, and once the regrowth starts, the curl will start there too, although the part that has been straightened will generally stay pretty frizz free. It is a fairly damaging procedure to have, dries the hair out alot, weakens it and it breaks easier... but if you look after it well, it shouldn't be too bad. I have been getting mine done every year and a half, but am giving it a rest after a few years of this. This is probably the closest to a "permanent" fix as you are going to get. Bear in mind that it can also be expensive.
Hope this helps!!