The frequency is a measure of oscillating charges; it is defined by signal source.
Wave length is a parameter of electromagnetic wave with a given frequency, measured along the line of propagation. If the wave propagates in air or vacuum, the equation c = f. lambda is valid , where c is the speed of light in vacuum.
If you propagate the wave in another medium or in a transmission line, c is different by that medium (permittivity) and/or by the structure of the transmission line.