TAT-1
The first transatlantic telegraph cable had been laid in 1858 (see Cyrus West Field).  It only operated for a month, but was replaced with a successful connection in 1866.  A radio-based transatlantic telephone service was started in 1927. It charged £9 for three minutes.  A telephone cable was discussed at that time. But it was not practical until a number of technological advances arrived in the 1940s.