I'm not familiar with their hair, so not sure what type of keratin tip they use.
If it is italian keratin then pure acetone wont touch it, you would need an alcohol based remover solution
If not italian keratin then pure acetone, available from the likes of salon services, will remove them.
You just need a small bottle with a spray nozzle - squirt some on the bond and work in with fingers, crush bond with pliers and continue crushing until keratin becomes powder like. Then just ease the extension and bond out
Hope this helps