Lo sentimos, no puedes realizar un pedido por Internet en este momento

I would assume they would check that also, but it could be a small detail that they may not have noticed, so they didn’t bring it up. 

The fact that it only happens when you are adding a phone line instead of a "mobile internet" line (just what we call anything that has service that isnt a phone), suggests to me that it has to do with line count or plan type. I don't think it is anything to do with your access permissions on the website because those other orders would be affected to. I could be wrong, but I have been doing this a long time and that is my hunch. 

I can understand if you are apprehensive about sharing your plan name or number of lines on a public space, so if you want to DM me, you can. It would be best for me to know how many teléfono: lines you have on your account and your plan name, so that I can rule those out as the issue. If you could also share the promotion you were looking at, I can see if we still have similar stuff going on so you can still save big on cool stuff. :)