I believe the OP has the correct receiver.

He needs a 4 channel receiver. He states that he "assume one channel for the esc" which would then leave 3 channels for servos. He states he has 4 servos and I think he believes he needs 1 channel for each servo, thus thinking he needs a "5" channel receiver.

This isn't true, though. A 4 channel receiver is exactly what he needs.
1 channel for the ESC
1 channel for the rudder
1 channel for the elevator
1 channel for the ailerons using a "Y" cable.

This will work perfectly with a 4 or more channel transmitter.