We experimentally insert a flexible number of electro-optical (EO) comb lines into a Kerr frequency comb via EO modulation and demonstrate the use of combined Kerr and EO combs as light sources in coherent communications. The number of EO lines inserted into the Kerr comb can be varied by changing the modulation frequency. Additionally, the inserted EO comb is found to have similar coherence to that of the Kerr comb, as indicated by their linewidths. The high coherence of both the Kerr and EO combs has further been demonstrated in a communication experiment in which the comb lines are encoded with 10 Gbaud quadrature phase-shift-keyed signals. The increased number of comb lines after EO modulation indicates the possibility of obtaining more data channels in optical communications.