In English, if I am spelling my name for someone over the phone I can use a phonetic alphabet to ensure they get my name right. Especially for potentially ambiguous letters; d and t, b and p, c and e, ...
I've hear on many occasions that Chinese prolong the last word in a sentence, for example: ni hao ma ? becomes ni hao maaaaa ? (I'm not sure that's clear enough but can't think of a better way ...