You`re dealing with heavily-processed [ acid-bath] hair..the cuticle [outer] layer of hair has been stripped off and the hair then dyed/coloured...such knotting and poor texture is a sure sign of harsh processing. You`re doing nothing wrong, as such.... it`s simply down to processing.
Try a little Brylcreem [original] on it...just a small amount, or some leave-in conditioner, which can help a bit, but you really need to get/have Remy hair. http://www.toplace.com/why-choose-toplace/quality