import problem

hello together,

I imported our complete client and contact list from excel (we worked with another CRM). at first I imported the client data then I imported the contacts because I can't do it in one step. the problem is that we have up to 10 clients with the same name. and now the second import of the contacts of the clients goes wrong because the contacts didn't match correctly. I found in one client all the contacts from the other clients.

now my question: is there any possibility to match them correctly by using a second field like "adress" or a clientnumber (we have them) or anythning else ... and what would I have to do while importing our data from excel? would it be a way to check one field e.g. clientnumber as "obligate" ... does it work then in the right way?

sorry for my bad english I'm from germany.

thank you for your help!!
gordon