How would you correct the faulty pronoun reference in the sentence I asked about the warranty but they weren't able to help?

The faulty reference is using the pronoun 'they' with no antecedent. The sentence must be reWorded, for example:

I asked about the warranty but no one was able to help.I asked the sales clerk about the warranty, but he wasn't able to help.

Note: The indefinite pronoun 'no one' does not require an antecedent.