You were absolutely not lied to, the TV supports Teletext. The sales person told you the truth. If you're angry - be angry at the TV stations that have stopped supporting/supplying Teletext - why you wish to blame a poor sales person is beyond me. I cannot even fathom the stupidity of this post, seriously you need to go look in the mirror and realise you're entirely wrong and out of line.
Also - no young person uses teletext these days, they probably havent even heard of it. The sales person would have correctly checked the specification listing on the TV. The last time I personally used Teletext was in 1994, when I was curious. TV's these days are SMART TV's which support internet, the new Teletext - you need to get with the times.