Extra fees hidden by salesgirl at purchase

Has anyone (everyone?) noticed this situation: I purchased an iPhone SE at half price. The sales girl told my son that it came with a case and tempered glass. Later, I found out that the charge for the case and the glass (each $39.99) were added to my bill to be paid off in 24 months. There is absolutely no way I would have agreed to this as I barely could afford the half priced phone. We went to the store and asked about it and the rude manager said there's nothing she would do about it. This is false misrepresentation.

Different topic- How do our SyncUp Kids watches go from $10 a line to $12 and now $17 without notification? It was established for a 24 month auto draft. Do they just raise line charges whenever they want.

Getting very frustrated with T-Mobile