I purchased this phone in December 2018 and have had nothing but bother with the battery it won’t last longer than an hour off charge. This is no good whatsoever. It’s still within warrenty and I’d like help sorting this problem.
Have a look here for details on how to return your phone...
If the phone was brand new when purchased then you have manufacturer's warranty which you may be able to access locally.
It the phone was refurbished or pre-owned then warranty is return to giffgaff only.
I would be surprised if any online phone seller provided a loan phone for the period of any warranty repairs.