Keep the context of the request
If the integration passes an ad ID or link, store it as a separate field. For manual input, use an agreed source and a specific offer. Do not record all enquiries simply as "internet": this makes it impossible to compare channels.
Continue with: UTM in CRM: preserve the source of an enquiry.
Consider different methods of contact
A message may contain a direct link to an ad, whereas a regular call may not. A separate number helps identify the channel, but not always a specific ad. UTMs work only where there is a suitable transition and the parameters are preserved. Don't attribute accuracy to a system that its data doesn't support.
Continue with: Website leads in SalesDrive: field mapping and acceptance.
Compare costs with quality
Compare approved placement and promotion costs with qualified leads and sales. Separate duplicate, repeat purchase and new need. Verify that managers fill in the source and reasons for lost leads in the same way. Flag unattributed enquiries in your report, rather than randomly distributing them between campaigns.
Continue with: OLX business profiles: prepare listings and enquiries.
Is it possible to calculate the exact return on investment for each ad?
Only if there is a sufficient connection between the costs, the announcement and the result. If some of the requests do not have this relationship, the report should show this limitation.