Bad service

I made the cell number prepaid as we were still receiving calls on the number and all the business cards and advertising is on this number. From a few days ago we were suddenly not receiving any calls and no longer have access to the what's app. This number is the one all the customers contact us on and all the years of advertising is on this number. It now appears that the number has been given to someone else and the Watts app cancelled. I was assured when I mafe the number prepaid that this would not happen. We are still in the process of settling my late husbands estate and my son is managing the business. The customers are now unable to get hold of us. The business cards and adverting on the website have cost us thousands over the past 15 years and I cannot afford to loose this number. We were also not informed that they were planning to take the number as we have been receiving calls hover not making calls while waiting hor the estate to be sorted out