This app was mentioned in 3 comments, with an average of 1.67 upvotes
What the brother MarriageOnly said is pretty much all that needs to be said.
Except if I may add a few not to make you feel overwhelmed but for knowledge and awareness sake so you can attain stronger eemaan. If this friend is a non Muslim...
We are forbidden to take the disbelievers as close intimate friends/allies. Allah and his messenger have warned us in Quran and Hadith to not take dibelievers as allies. One proof is
It is confirmed that the Prophet sallallaahu `alayhi wa sallam ( may Allaah exalt his mention ) said: "Do not keep company except with a believing person." [Abu Daawood].
However if this person sends you a message I think you should be straight forward and tell them look we can't maintain this relationship. Invite them to Islam and maybe leave them with some good sources. If they accept Alhamdulillah if they don't then there is nothing you can do as Allah guides whom he wills.
If they are Muslim then well cutting it off completely is the right thing to do. In fact it might not be hard since you are not attached to the point where you message each other everyday. Alhamdulillah.
Also I'll leave you with a few duas although I don't know of any dua to ask for good company I say these often رَبَّنَا آمَنَّا فَاكْتُبْنَا مَعَ الشَّاهِدِينَ Our Lord! We believe; write us down among the witnesses. Surah Al-Ma'ida - 5:83
When entering/exiting a town وَقُلْ رَبِّ أَدْخِلْنِي مُدْخَلَ صِدْقٍ وَأَخْرِجْنِي مُخْرَجَ صِدْقٍ وَاجْعَلْ لِي مِنْ لَدُنْكَ سُلْطَانًا نَصِيرًا And say, "My Lord, cause me to enter a sound entrance and to exit a sound exit and grant me from Yourself a supporting authority." Surah Al-Isra - 17:80 https://play.google.com/store/apps/details?id=com.arshan.dhikrdua
Btw download that app alsoit has lots of duas :) I hope you benefit Insha Allah
Dua at times of worry & sorrow اللّهُـمَّ إِنِّي أَعْوذُ بِكَ مِنَ الهَـمِّ وَ الْحُـزْنِ، والعًجْـزِ والكَسَلِ والبُخْـلِ والجُـبْنِ، وضَلْـعِ الـدَّيْنِ وغَلَبَـةِ الرِّجال O Allah, I seek refuge in you from grief and sadness, from weakness and from laziness, from miserliness and from cowardice, from being overcome by debt and overpowered by men (i .e . others). Al-Bukhari 7/158. See also Al-Asqalani, Fathul-Bari 11/173 https://play.google.com/store/apps/details?id=com.arshan.dhikrdua
The best Du'a app in my opinion. Comes with references and so many du'as!: https://play.google.com/store/apps/details?id=com.arshan.dhikrdua
The best Quran app at the moment is probably this one as it comes with English translation from Saheeh International and Mishary playback so you can follow the ayaat without having to scroll: https://play.google.com/store/apps/details?id=com.guidedgeeks.guidedverses