30 - 50
or 50 - 100

That's the normal speed for 30Mbps, we call it Club 28 here.
Nope, you can't complain. I complained before and technician came and said it is normal. TM's promised speed is 80% which is 24Mbps and even MCMC stated 90%, that's 27Mbps and 28Mbps is above both requirements.

If you complain now, it will charge you RM 53 for technician to come to your place. When I complained mine, this thing wasn't effected yet.

So live with it.

50Mbps is Club 47 by the way.