Invesco Junior Java Developer interview questions

I applied for the junior java developer position in Frankfurt. I got a telephonic interview invite and job description. Job description was very canned and was surely describing a java role. One wierd thing was that they asked me to dial for the telephonic conversation. On the interview day when I dial the number it says that the number is non existent. Time passes and I am waiting for someone to call me. I also reached the HR throughout which after some time that there was some miscommunication. After half an hour they managed to somehow call me and to my surprise, the job required knowledge in C# and R for statistical modeling. At this point I was totally confused what is happening with me. The telephonic turns to be fine and then they gave me a lengthy assignment with a week time limit. I completed the assignment and gave it to them. 2 weeks pass and nobody came back. I asked for the feedback of my candidature and the HR doesn't respond. Probably they might have found a suitable candidate which better matches for C# and R role. I can accept the rejection but nobody coming back to you once you have invested entire week to solve their assignment is harsh and rude. After all the chaos, after 3 months I randomly get a mail which says that they have a feedback for me in early January after the December vacations. Entire January has gone, and there is no feedback mail. After all this I just want to say that being a company they should not toy with the candidates. I urge everyone not to apply in this malfunctioned company.