I have some doubts. Only small or weird outlets have any news on this and there is no good original source linked anywhere.
The Canadian Press explains a potential path by which this claim could have arisen, namely that Slim's company América Móvil had stated in an earnings call that they were going to invest 22 billion pesos (! not USD) in infrastructure over three years and they didn't have plans to invest it in Starlink, instead looking more towards two other satellite companies, and only for rural backbones where laying fiber would be more expensive.
I hope he feels worse soon