How can I calculate the height at which the mobile phone is located?
That model is used to estimate path loss based on distance and frequency (applicable to RF frequencies from 150 to 1500 MHz). Since there are an infinite number of heights that would resolve to the same distance, you cannot use the formula with the transmission from a single BTS to resolve the mobile height.
You could theoretically triangulate this with multiple transmissions from multiple base stations but given the variance in the actual land-based propagation models there would be significant challenges in achieving any sort of reasonable accuracy.
Why not use GPS since nearly every mobile has a GPS receiver now?