They consider it a favor to you that they have accepted Islam. Say, "Do not consider your Islam a favor to me. Rather, Allah has conferred favor upon you that He has guided you to the faith, if you should be truthful."
يَمُنُّونَ عَلَيْكَ أَنْ أَسْلَمُوا ۖ قُلْ لَا تَمُنُّوا عَلَيَّ إِسْلَامَكُمْ ۖ بَلِ اللَّهُ يَمُنُّ عَلَيْكُمْ أَنْ هَدَاكُمْ لِلْإِيمَانِ إِنْ كُنْتُمْ صَادِقِينَ