I think the answer by Eri san is right. I would add a little supplement. I think here the usage of 接触 is the point. You know, 接触 can be a verb and a noun. If 接触 is used as a verb, we usually say without using の, like ご本人"と"接触しました. …> One contacted(V) with the identical person If 接触 is used as a noun, we usually say with using の, like ご本人"との"接触に成功しました. …> One succeeded in contacting(N) with the identical person So bothと and との mean “with”. But と is for the use with verb, との is for the use with noun. Though I am not specialist of grammar, they might be regarded as an adverb use and an adjective use respectively. Happy if this helps.

It was successful that I come in contact with the person. "との" →with