So Elliot sold all of their AT&T position. They also sold much of the rest of their portfolio. They also bought a very significant number of ETF QQQ Put Options. QQQ is a large-cap growth ETF with large positions in the FAAGM stocks (Facebook, Apple, Amazon, Google, and Microsoft). A Put option gains in value when the underlying stock declines in price.
In short, it appears that Elliot believes the market is going to hit the skids, especially the high momentum FAAGM stocks that have gained the most in the past six months. They may have sold out their AT&T position as part of their belief that an overall decline in share prices, including T, is imminent.
That doesn't mean they are not going to have a new significant position in AT&T in the relatively near future. They don't give up that easily.