When is AT and T buying t-mobile?

No. But there are rumors that AT and T will buy out T Mobile.

AT&T attempted to purchase T-Mobile on March 20th, 2011 for the proposed amount of $39 Billion. The bid was later abandoned by AT&T in December of that same year after the US Department of Justice announced that it would seek to block the takeover, and filed a lawsuit to such effect in federal court.

T-Mobile lost over 700,000 subscribers in 2011, primarily due to the availability of the iphone with other carriers. Since then, T-Mobile has re-grown it's customer base, adding 4.4 million users to its 2013 numbers, due in part to their acquisition of Metro PCS. They've even landed a spot on a list of the most innovative companies of 2014.

This, in combination with the roll out of their Modernization equipment, which combines CMDA/GSM and LTE antennas for 2G, 3G, 4G LTE and data compatibility is keeping them in the game.

For now, it looks like T-Mobile is here to stay.