This is definitely considered heretical. Our denomination broke from other pentecostals over this issue (the oneness folks) in the early part of the previous century. The downside of protestantism (one of em, anyways) is that we have to fight all the heresy battles all over again.
Each church is a voluntary cooperating member of the Assemblies of God. However, in order to belong, one must adhere to our 16 fundamentals of faith where the Trinity is explicitly stated as a fundamental doctrine (Fundamentals of Faith here). If the pastor is teaching this, his license should and can be removed immediately. Further, if the church chooses to follow this belief, their participation in the AOG would be revoked. I seriously doubt that this is being taught at an AOG church, but far stranger things have happened. :(
Just as the Assemblies of God have 16 Fundamentals of Faith that must be adhered to, so too, does the Catholic Chuch have dogmas that must be adhered to in order to be a Catholic. That is why the Canon of the Bible is so important. It is one of those fundamentals that must be believed by all believers. Thus, when Luther, of his own accord, removed books from the established Canon of the Bible, he stole from all succeeding generations of Protestants, Fundamentalists, etc., their patrimony.
I seriously doubt that this is being taught at an AOG church, but far stranger things have happened. :(
I sincerely hope that they are not teaching this, as the doctrine of the Trinity is one of most beautiful of Christian teachings.