How can I connect a T568 cable to a 4p4c jack?
Phone lines only use a single pair.  As long as the same wire goes to the same pin on both ends of the RJ11 connector, it will work. Standard pair colors are black/yellow and red/green.  A single line uses the two middle pins of the RJ11 connector, but two-line phones will use the inner and outer pairs.

T568A/B only applies to Ethernet connections.