If your phone is not holding charges, then apple will replace the battery free of charge if the phone has no sign of damage such as broken screen or or water damage. If such damages occurs, apple is likely to suggest that you back your device throight iTunes or icloud because they will take your broken phone and give you a new one right on the spot with a fee of course(I forgot the amount) Otherwise they charge $29.99 for a new battery replacement
Regular store. Same as all.
Try to go to help and support they might be able to help you
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