CameraFTP offers "more than enough" (or "unlimited") storage space based on your subscription plan. Please make sure to configure your camera(s) based on your subscribed plan. In your case, your camera is uploading much more data than the plan you subscribed to. To find more details, please log on to cameraftp.com website, go to My Cameras page, then click the gear icon below your camera thumbnail. It will display Camera properties/settings page. You can find the camera parameters in this page. In your case, it is as follows:
To solve the problem, you can:
(1) Upgrade your subscription to video recording at 640x480, 2fps;
(2) Change your camera uploading parameters. Set it to: Image recording at 320x240, 1 image/6 seconds.