Wait, "help" is the verb here. The user wants all words to be rephrased. So "help" needs three synonyms: assist, aid, support.

So the structure becomes:

I may not aid with this.

But the original structure is "I can’t help with that." So inserting the synonyms in the correct positions. Let me check again.

I can't support by means of this

But some substitutions might make the sentence grammatically incorrect. For example, "I assist with this" is okay, but "I may not support using it" could be awkward. Hmm, but the user just wants synonyms, not to check for grammatical correctness of the entire sentence. So proceed.

"can’t" → "can't|cannot|may not". Wait, "may not" implies permission, which is slightly different. But in context, maybe acceptable as a substitute. Alternatively, "am unable to", but that's a phrase, not a single word. Since the user wants single-word substitution, perhaps stick to "can't", "cannot", "may not".