Feeling cheated yet again

Just about every time I make a change to my account I end up paying way more than what's presented by the agent. This time around I switched my lines from by the gig to unlimited thinking i would pay about $60 as he had said. But turns out he only moved one line instead of two and didn't delete the third one. So I paid about $20 more for 3 months before I realized the mess up. Got another agent to make the adjustment I asked for but apparently since I made the change on my billing day I have to still pay $35 extra for a by the gig plan that I was on for a few hours in the new billing cycle, which means I'm out about $100 for a change that was supposed to save me money. This makes no sense to me. Honestly, at this point google or tmobile would probably be better. It was convenient and made sense years ago when I signed up. Now I'm just losing money.