Whatsapp limiting network usage?
There was and possibly still is a restriction on message forwarding but there is none on data usage.


  WhatsApp has announced it will restrict the number of times an individual message can be forwarded.


The only restriction on video is about the size. When it is larger than 16MB then you need to reduce it.


  If you choose to send an existing video, it is limited to 16 Megabytes. On most phones, this will equal about 90 seconds to three minutes of video. If you choose an existing video that is larger than 16 MB, then you will have the option to trim the length of the video before sending it. 


You should check if data limit is set or not on the phone. Go to Settings -> Data usage -> Cellular data usage. Clicking the gear, should show you the data limit and if it was set or not.