I still use the first iphone but now battery is not holding charge. Can I get battery replaced?

I still use the first iphone but now battery is not holding charge. Can I get battery replaced?

Yes. It's not cheap, however.

It will be very expensive to have the battery replaced by someone else but you can do it yourself by following the below video.

Yes. But it will be costly

It makes more sense to replace than repair at this point, meaning get a new phone rather than trying to fix up that one.