be动词的否定用法I wasn't answer the phoneI wasn't answering the pho

e动词和一般动词否定是不一样的,be动词的否定式是直接在be动词后面加not,一般动词后面不能直接加not,需要借助于助动词do、does、did再加not,助动词后面一定用的是原形动词,如：
I didn't answer the phone.
I wasn't answering the phone.
助动词be与现在分词、过去分词构成进行时和被动语态,助动词do与动词原形,构成一般现在时、一般过去时的否定句、疑问句和倒装结构.如：
Are you eating your lunch?
No,I am not eating my lunch.
Did he do his homework?
He didn't do his homework.
Often does he give me some useful advice.
希望我能帮助你解疑释惑.

be动词用于系表结构句，或者进行时。do用于实义动词的一般现在时。
你的第一句错了，应该是：I don't answer the phone.不过也有点怪怪的，还是用I didn't answer the phone.好些。