When you start, plate the cells in your normal medium.  Once they have settled, change the medium to the stripped FBS/phenol red free medium and incubate 48 hrs before starting an experiment.

Hello, phenol red is highly unlikely an issue. 

Rather it could be either the chosen serum or the coating of your plate that's causing the problem. 

I recommend you use Corning Costar (brand) plates, which are pre-coated and ready to use.

As for FBS, unless charcoal treatment is absolutely necessary and unless your work is based on published methods or a labmate's routine, it does not seem to be something necessary for culturing or maintaining common breast cancer line like MCF-7.

ATCC did not recommend such specific use of FBS. 

If you are concerned with microbial contamination, just buy normal serum and do a heat inactivation step in lab. 

It is far more common to use heat inactivation than charcoal for disinfection.

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next time, after plating cells onto 24-plates, observe after 1-2 h if they can properly attach at all. 

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Protocols:

http://www.hiv.lanl.gov/content/nab-reference-strains/html/Protocol-Heat-Inactivation-of-Plasma-and-Serum-Samples-December-2011.pdf

http://www.signaling-gateway.org/data/cgi-bin/ProtocolFile.cgi/afcs_PP00000127.pdf?pid=PP00000127

Yes, it is most likely the FBS in this case. The absence or presence of phenol red isn't going to make a difference. (Also not going to make a difference for the MTT, so unsure why you're using phenol red free in the first place). What is the reason you're not using normal FBS?

Agreed, Phenol red act as pH indicator its not going to harm your cells, Check contamination most probably Mycoplasma in your culture and source of FBS

Reason for using phenol red free and stripped serum in the MCF7 E-screen assay (see papers by A Soto) is due to the fact that phenol red and estradiol/estrone/estriol in serum interfere with the E-screen assay. 

Thank you all very much for your answer and help! I do really appreciate.

 Try to add L-Glutamine (final concentration in medium 2 mM). You also need to supplement the medium with Sodium pyruvate.

Probably a contamination with mycoplasma, it do the test about it. In case positive, then mycoplasma can be in the FBS

As you know, MCF-7 have estrogen receptors and are estrogen dependent for growth. In conditions of charcoal-stripped FCS, which removes not only steroids but also other factors, and with no phenol red, which is weakkly estrogenic, the cells are deprived of sufficient estradiol etc to maintain their viability.

May I refer you to two publications, which describe how I cultured MCF-7 cells under E2-deprived conditions:

A one minute pulse of estradiol to MCF-7 breast cancer cells changes estrogen receptor binding properties and commits cells to induce estrogenic responses

Angela M. Otto The Journal of Steroid Biochemistry and Molecular Biology 08/1995;

Chemotherapeutic drugs change actin skeleton organization and the expression of β-thymosins in human breast cancer cells. A M Otto · C S G Müller · Huff T. · Hannappel E. Journal of Cancer Research and Clinical Oncology 06/2002;

Thank you all your help.

I am still working on this issue. Yes, as Edmund Pool said above the reason using phenol red free and charcoal stripped in the MCF7 E-screen assay is due to the fact that estradiol/estrone/estriol in phenol red and FBS interfere with the E-screen assay. But I followed the prototol from my collegue, maintaing the MCF-7 cells in phenol red medium, then seeding cells in the Charcoal stripped FBS/phenol red free medium. He said that it worked before. We are doing everything as what he has done, but all cells cannot attach and dead in the flask or plate with charcoal stripped FBS/phenol red medium.

We also tried to change the medium to the stripped FBS/phenol red free medium and incubated 48 hrs before starting an MTT assay. all cells were dead in the flask or plate with stripped FBS/phenol red free medium.