The OP stated that he was using the XFS filesystem. The tool resize2fs works with ext2, ext3 and ext4 only.
There’s a similar tool available for the XFS filesytem called xfs_growfs. You’ll most likely have to install it first
sudo yum install xfsprogs.x86_64 --assumeyes
then mount your filesystem
sudo mount -t xfs /dev/sdf /vol
now you can extend the filesystem
sudo xfs_growfs /vol
df -h should now show more available space
I hope this helped 🙂
Tip: ext4 filesystem is the recommended filesystem for EBS volumes ( for the future )