::::::::That's not true. An allophone can only use phonetic information, not morphological (part-of-speech) information. What you are describing is morphophonological alternation. 
 ::::::::The definition of "phoneme" is "the smallest segmental unit of sound employed to form meaningful contrasts between utterances". That means that if the alternation between /d/ and /t/ indicates whether a word is a noun or a verb, then the difference between /t/ and /d/ indicates meaning, so it is phonemic. I can explain this further or give you more evidence, but I will just tell you that you are misusing the words "phoneme" and "allophone".