Why do you want to leave your current position?
If your current or last position was or is so good, why do you want to leave? It's a good question for an interviewer to ask.
Never be negative about your employer, the interviewer may get the impression that if you left their company one day you would talk badly of them.
For this reason it's best practice to be possitive. Every role has boundries, maybe you can only manage national accounts or work in a small team. Turn these into future psitives by telling the interviewer that you have a personal and professional goal to work in a larger team or that you wish to manage an international clien't portfolio. Either way you should sound ambitious and demonstrate that you want to compliment your experience and that you have the want and need for more scope in your sector.
Remember that you are one of many candidates who all have similar academic backgrounds and experience. If you want to be the best and stand out from the crowd, you will have to practice your answers and eliminate the competition.
So how would you answer this question based on your work history?
You need to practice this answer carefully using all the tools available to you:
Voice tones
Grammatical structure
Vocabulary
Speed of speech
Pronunciation
This answer will be recorded for you, so that you can practice outside of a classroom environment.