When I plug my z to pc, loop happens "plug and unplug"

Dear sir,

at the beginning when i unplug-ed the cable from my xperia z the pins came out, i tried to charge from the dock socket with the cable it charged till i entered the wire wrong, i gave it to the service they change the socket and fix the problem, but the dock didn't work, i can charge it from the charger but when i plug the device to the pc loop happens "plug, unplug, plug, unplug"! i tried 3 different computer with 5 different cable ,when i connect the charger it work well,

any help please