iMessage issue after Switching to android

Ok so i like to switch between my iphone and android phones throughout the week. This is my first iphone so i'm not sure how to correctly go about this iMessage issue when switching. Let me tell you what I am doing. Before I switch sims, I turn off iMessage/Factime. I wait a bit, send a message to make sure the bubbles are green (they are). Then I swap the sim over to my android phone. I will receive texts from people with iPhones....but group messages are a hit or miss. Some group messages, i'll get a text from an iPhone user....others I wont. So then i've tried to go onto my devices page, and remove my iPhone. No luck. i'm tried the deregister page, but NEVER get the text that says "sent". Ever. On either phone, with iMessage on or off. I've tried changing my iTunes password, logging out of everything on my iPhone. Nothing. I know i'm a rare breed who likes both OS's, but I like to switch phones....and I hate feeling like apple has my number hostage in the iMessage system. I love it....but hate this part of it. I just want to seamlessly switch with no issue. I tried contacting apple, who told me it could be a SIM issue. AT&T told me what everyone else says, that Apple has this issue and has pending lawsuits going on with no workaround in site. But I see other people getting this to work. So.....

What am I doing wrong????