When you create an instance, the instance is automatically attached to a virtual network interface card (VNIC) in the cloud network's subnet and given a private IP address from the subnet's CIDR. You can let the IP address be automatically assigned, or you can specify a particular address of your choice. The private IP address lets instances within the cloud network communicate with each other.
Reference:
https://docs.cloud.oracle.com/en-us/iaas/Content/Compute/Tasks/launchinginstance.htm Instances use IP addresses for communication. Each instance has at least one private IP address and optionally one or more public IP addresses. A private IP address enables the instance to communicate with other instances inside the VCN, or with hosts in your on-premises network (via an IPSec VPN or Oracle Cloud Infrastructure FastConnect). A public IP address enables the instance to communicate with hosts on the internet.

A shape is a template that determines the number of CPUs, amount of memory, and other resources that are allocated to an instance.
The network bandwidth is directly proportional to the number of OCPUs in the instance shape!

You can open a support service request with Oracle Support
To create a service request:
Go to My Oracle Support and sign in.
If you are not signed in to Oracle Cloud Support, click Switch to Cloud Support at the top of the page.
Click Create Service Request.
Select the following from the displayed menus:
Service Type: Select Oracle Cloud Infrastructure from the list.
Service Name: Select the appropriate option for your organization.
Problem Type: Select your problem type from the list.
Enter your contact information.
Enter a Description, and then enter the required fields specific to your issue. For most Oracle Cloud Infrastructure issues you need to include the OCID (Oracle Cloud Identifier) for each resource you need help with. See Locating Oracle Cloud Infrastructure IDs for instructions on locating these.
Reference:
https://www.zerowait-state.com/blog/create-sr/