If you are an end user receiving calls from a number starting 08979 then the issue is most likely with your own service provider. Please raise it with them in the first instance, explaining that you are seeing "Network Numbers" instead of "Presentation Numbers" on your inbound calls, and refer them to this article.
08979 numbers are intended for use by telephone networks to identify the origin of a call, they are sent as underlying "Network Numbers" and shouldn't be presented to the recipient of the call.
If you are receiving calls from a number starting 08979 01 then please contact email@example.com providing details of the date/time of the call, your own number, and the network that provides your phone service. If you're using a mobile, the type of device you have may also be relevant.
The new regulation came into effect 1st October 2018, and all networks and service providers had over eight months to prepare for this.
Guidance Note for Communications Providers
We have received reports that some providers are passing numbers starting 08979 to their end users. Where these calls have originated from Simwood, the number will start 08979 01. In each case there will always be a Presentation Number in additional to the 08979 number, this is the number that should be presented to the end user as per ND1016;
Presentation Number (when available) is used in preference to the Network Number of the calling or connected party. This is important where the Network Number is not suitable for display, e.g. where PABXs have segregated incoming and outgoing lines.
If you are a TDM connected CP, you will see this as the Generic Number (Additional CgPN) in the IAM message.
If you are a SIP-connected CP, for example using an IP Exchange product, you will see this as the number in the From header of the SIP INVITE.
The Ofcom guidance can be found here which states;
3.77 In most cases, the number presented to the recipient of the call should be the Presentation Number. Although some calls will have a different Network Number and Presentation Number, in many situations for legacy networks and in some SIP calls, the Network Number and the Presentation Number may be the same number. Where calls have the same CLI for the Presentation Number and Network Number, CPs must be mindful of the requirements for both types of numbers
These regulations came into effect from 1st October 2018, but it's apparent that many CPs are not yet complying with them and this is likely to cause considerable consumer confusion as calls are being presented to end users from numbers they can't call back, contrary to Ofcom's intention to improve the situation by reducing consumer harm as a result of "spoofed" CLI usage.
If you have any questions regarding this, or calls originating from our network, please do not hesitate to contact firstname.lastname@example.org