别用你那没断奶的声音说话
[bié yòng nĭ nèi méi duàn năi de shēng yīn shuō huà]
Do not speak with your childish, milk-fed voice. Here it shows an irritation or annoyance towards someone immature. It's a slightly rude or dismissive way to express that someone should be more mature or serious when speaking.