How to increase only network transfer quota. I don't want to Resize Linode

For some clarification, unlike the CPU or RAM provisioned for any sized Linode, our Network Transfer Allowance is not a hard limit. There is no way to increase any plan's transfer limit, because reaching that limit will not stop outbound traffic.

If you exceed your monthly transfer allowance, you are merely charged a range of $0.005-$0.015 per GB (or $5-$15 per TB) based on the data center. Since your allowance is treated as a pool, all Linodes deployed to your account share a combined total of transfer allowance. This means that in certain circumstance where you anticipate consistently exceeding your allowance, it might be more cost effective to deploy additional Linodes.

Thanks for the quick reply @jhartman