Nǐ wèishénme bù jiē diànhuà?
你为什么不接电话?
Why didn't you get the phone?
Notes:
你(nǐ): you
为什么(wèishénme): why
不(bù): not
接电话(jiē diànhuà): to answer the phone
Example:
A:你为什么不接电话?
Nǐ wèishénme bù jiē diànhuà?
Why didn't you get the phone?
B:我没听见。
Wǒ méi tīnɡjiàn.
I didn't hear it.