Intro
It’s very true, lots of Muslims from the Indian sub-continent call Ahmadi’s as Mirzai’s.  Nowadays, Ahmadi’s hate being called Qadiani or Mirzai and cry persecution whenever someone calls them as such.  However, back in the early days of Ahmadiyya, Ahmadi’s never had a problem with word Mirzai, in fact, we have a scan from the al-Badr Qadian, 7th January 1907 during life time of Mirza Qadiani, wherein an Ahmadi proudly calls himself a Mirzai.

Summary and brief translation of this scan and reference
A follower of Muhammad a muslim was called as Mohammadan by britishers.

See the red highlighted area of this scan, a Qadiani poet says “”Hum Hain Pakke Mirzai”” (we are hardened Mirzai).

This poem was read over by Mir Qasim in Jalsa salana Qadian and published in the al-badar .

The scan

Other related essays
https://ahmadiyyafactcheckblog.com/2016/08/10/wonder-why-we-call-them-qadiani/

https://ahmadiyyafactcheckblog.com/2018/01/29/qadiani-ahmadis-vs-lahori-ahmadis-sectarianism-within-ahmadiyya-2018-version/