Is there a website or service that combines databases?

I have located an older database, manual and mailchimp, containing 15000 contacts. Is there a combined website or service that offers a combining of the databases so I can interact with the SMS and email? Any ideas would be great.

Lionel Yeo, CAIA

Lionel Yeo, CAIA, Co-Founder at Paperless Cloud Wesvault


Because of the field matching there's no 1 service migration. For 15,000 contacts is a little large for microsoft excel so you might need to cut it up into 5000 and use excel to piece it together.