"I have already complained twice to the telephone department." Which word used in the sentence is the adverb of frequency?

The part of a sentence that speaks about the action of the noun is known as the verb. On the other hand, the words that give more information about the verb are known as adverbs. An adverb can be of several types, depending upon the function performed by them. One of those types is the adverb of frequency, which tells how frequently or how often an action is done. In the sentence, "I never get late to work," the word 'never' is an adverb of frequency. Likewise, in the sentence given in the question, the word 'twice' is an adverb of frequency.