refurbished iphone 6s

If you want an Apple OEM refurbished device with a standard one year Apple warranty (and eligible for AppleCare+ where offered), then you have to buy it from Apple directly. Other “refurbishers” (read their fine print about exactly what they mean by refurbishment) offer their own warranties and are not covered by Apple (e.g. Amazon refurbished devices are refurbished by Amazon or their contractor, not Apple, and have no warranty from Apple).

Directly from Apple online or an Apple store. Do not get one anywhere else.