Well, it seems to be pretty good as it is. I would suggest a few grammatical changes, just to make it flow a little better. Also, I don't know if you're trying to be overly polite in booking the tickets, but people don't tend to be so formal when buying things over the phone, but that isn't really important for homework like this.
J'aimerai should be translated, and the sentence should be condensed a bit, so it would be something along the lines of "I'd like to have two seats for my friend and me, next to each other and in the middle, if possible."
Near the end, one of the responses is written as "Just a second, I seek. Viola." It should be rearranged slightly so it flows better, so something like, "I'm looking for it, just a second," or just "Just a second." The "I'm looking for it," or "I seek," as you wrote it, is often implied. "Viola" can stay, if you'd like, or you could say, "Oh, I found it," or "Here it is," if you use the implied version.
Below that is the phrase "All is perfect..." This seems a little weird to me, so I would suggest saying something like, "It's all good," or just "perfect."
When thanking the person over the phone, most people don't use the title "Madam." Just a simple "ma'am" or "miss" would be used, or no title at all, just "Thanks."
I hope this helps!
