Use 'either'. Because most of the time English does not use a double negative expression. 'Neither' is considered a negative word for these purposes. "I don't hear you neither" is a double negative. It uses both 'not' (found in 'don't') and 'neither'. If you want to use 'either', you can say "I can't hear you either.' Notice that this does not contain a double negative. There is only one negative (the 'not' in 'can't').