Every number is stored in full international format, for example +918080197945, however it was typed: "8080197945", "08080 197945" and "+91 80801 97945" are the same person.
A number typed without a country code is read in your workspace's country. Change it in Settings → Workspace details → Country (owners and admins). The same rule applies to contacts, campaigns, the Do-Not-Call list and phone fields across the dashboard.