Maha, what does it mean كلام غير رتيب? It means that one has to change the tone by increasing or decreasing their voicesI'm confused. The sentence you gave is "have a non-monotone speak" (by the way, shouldn't it be 'speech'?) Buy the suggestions seem to be translating different sentences.
If you are still looking for a translation of 'have a non-monotone speech', then I would suggest: أن يكون كلامك غير رتيب or ألا يكون كلامك رتيبًا