Credit: Joe Maring / Android AuthorityTL;DRT-Mobile’s forced migration to Experience plans is causing some customers to lose long-standing free line promotions and pick up unexpected charges.One customer says promotional credits that were supposed to carry over have disappeared, turning some monthly bills from around $50 to more than $300.Some users also report free lines being deemed “ineligible” after the switch.T-Mobile’s latest push to force legacy customers onto new plans is officially underway and it’s turning into a costly nightmare for some customers. The carrier’s forced migration is apparently breaking long held free line promotions and secretly tacking on paid data add-ons.The carrier has recently begun moving users off of legacy plans such as Magenta, ONE, and Simple Choice onto its newer Experience lineup and has promised existing perks, including free lines, would be honored. That assurance has now been called into question after several customers said that their first bill post-migration lacked promotional credits.