There is a reality that prophets (messengers from God, who speak for God) came in and with God's authority (His name). Chiefly, a Prophet is known by their words coming to pass as announced. One of the indications of a prophet is that their message was confirmed by signs and wonders from God.

In the case of some OT prophets, there were not great signs and wonders, but simply the events they described coming to pass, as well as their declaration that they were speaking on behalf of God. 

Abraham - God spoke and acted on his behalf. Gen 19-20, God cursed those who came against him. Also, God supernaturally prospered him and protected him.

Moses - He directly performed signs and wonders.

For the other major and minor Prophets (Isaiah, Jeremiah, Daniel, etc) - They actually demonstrated their Prophethood in a different way. No signs and wonders, but all they stated did and will come to pass as announced. However, their message was inline with that of Moses, namely in regards to Deut. 28. When the people began to be rebellious Prophets of God spoke in accordance with the words given to Moses. They reminded the people of the words previously confirmed by God, namely, that the curses God promised for disobedience would come. They also spoke consistent with the blessings God promised because of the Deliverer (i.e., Jesus). This is key, because it gives us a precedent not only for knowing their message is from God, but evaluating other people's claims of prophethood.

Prophets today would speak on behalf of God, insomuch as they repeat what He has already said, not that they are given a new revelation from God. If that were so, then we can expect signs and wonders would accompany them to confirm that message. Like in the case of Moses, Jesus, Paul, Peter, etc.

What we see today, are subpar and earthly-quality expressions of prophethood. Namely, it is claimed they can be wrong sometimes, their theology does not have to be inline with the Bible, and no signs and wonders are needed to confirm it. Sounds like the false prophets of old, more than NT (biblical) prophethood.