Open Source Crm Software To Replace Sage And Excel?

Hi. I've got a client who needs to share a spreadsheet between two users. The spreasdheet contains about 10 years of customer job history, so they refer to the spreadsheet to see previous job costs and quotes before adding new jobs to the bottom line. The jobs involve materials, costs, quantities, transport, labour and other variables. They then re-enter the data into Sage later in the week !!!!

I've suggested they work directly with Sage, but they claim they've had no end of problems because Sage is cloud based and their internet is crap, so entering the data into Sage in real time doesn't work well and they only have a single user licence. The other problem is that the spreadsheet is about 12MB and anything over 5MB won't work if shared via onedrive and the web based excel, so we either reduce the working spreadsheet and lose historical data, or find a way of replacing the spreradsheet with something that works better.

In a nutshell, I need to find a program that I can import this spreadsheet into that can be accessed by two or more staff at the same time that will provide historical customer job details and allow new jobs to be entered and if possible, exported to sage or directly to invoice to replace Sage

If I could find a program that does this AND replaces Sage, they would save both the double data entry time and the cost of their Sage licence / support etc.

Can anyone suggest any low cost / free CRM programs that are worth looking at? The client is not very computer literate and doesn't like change which is how they've found themselves in this position, so a simple program would be easier to implement than a complicated all singing and dancing job.

Thanks in advance. Al.