You should check the lock. When you have 2 deuterated solvents is not easy for the NMR machine to lock on the solvent you choose. If you tell the machine to lock on DMSO and instead it picks the chloroform, every signal will be shifted! hope this help.

A mixture of two non protic solvents does not affect chemical shifts of the 1H NMR signals significantly, hence, you always can assign them to same species which, perhaps, were partially dissolved yet by application of each solvent separately. Surely, first of all, you have to be sure in the choice of correct lock signal (in your particular case you are dealing with two sorts of deuterium: in chloroform and in DMSO. If this was done yet, your result could be explained as follows. The different compounds present in your product have different solubility in the separate solvents and in their mixture. If you have no clues, which products you are dealing with and have problems with assignment of 1H NMR spectra, I could suggest you 1) to find some other appropriate solvent, 2) to apply 13C NMR spectroscopy, which allows more simple assignment of signals, or 3) the solid-state NMR spectroscopy (MAS), where you do not need any solvent.

Maybe we are going step back, but I must ask you two questions:

1) Did you try to dissolve your sample in DMF-d7? 

2) What is the ratio of DMSO-d6 and CDCl3 when you succeeded to dissolve your sample?  

The chemical shift is also solvent dependent, here is an interesting paper on the subject. The chemical shift difference from CDCl3 vs DMSO has been shown to be from -0.3 to +4.6 ppm.

http://www.modgraph.co.uk/Downloads/SCSpt23.pdf

FOr Biljana Arsic:

I did not try dissolving my sample using DMF-d7 because there were no DMF-d7 availablle in the laboratory, so i am opt to use DMSO-d6 and CDC3 mixture in a 1:1 ratio.

Thank you so much for all your suggestions, I have double checked the H1 NMR spectra, and also their corresponding C13 NMR. the carbon NMR turns out to be ok as expected because the structure of the products that were subjected to the analysis were known and had given signals that were intended for the signal of the supposed product. but for the H1 NMR analysis, I have double checked the peaks and it seemed like the technician running the NMR machine did pick the wrong choice of signal to lock on. instead of locking the signal for a DMSO-d6, the technician mistakenly locked that signal for a CDCl3 peak, that is why all the peaks that were supposed to be around 7-8 ppm were shifted to about 11-13ppm. i think that explains the shifted peaks. 

When you have one solvent, it is easy to perform NMR experimen(s) and interpret obtained spectra. If you take a look at dielectric constants of DMSO-d6 and CDCl3, you can see that they are 46.7 and 4.8, respectively. I suppose that your sample will be dissolved in DMF-d7, which dielectric constant is 36.7. Unfortunately, this solvent is not available in your lab. In your case, I suggest you to read and follow Bruker instructions (if you are using Bruker NMR machine).

thank you very much for the advice. 

Yes, you can have different shifts. That is why in articles always you have noticed in what solvent there was NMR analyse. Try to find articles with similar substances in different solvents, compare and try to find analogy.

NMR Spectrometer is generally equipped with lock corresponding to a pure deuterated solvent i.e. CDCl3 , DMSO-d6 etc. As you were using mixture of deuterated solvents, instrument remained unable to lock for the right / pure solvent.

i had the same problem for a semi natural synthetic product:

To answer how to get NMR spectra in a mixture of two deuterated solvents if it not available deuterated solvents in your lab:

for HNMR: Use similar nonpolar solvents without hydrogen instead of CDCl3. for example CCl4. in practice they do not very different to dissolve chemicals. in the other hand CCl4 is a cheap, passive volatile solvent to remove and recovery your product again. CCl4 has a 13CNMR around 95ppm

as an alternative you can use active carbon disulfide as a potent solvent , if your product doesn't react with it !!! CS2 has a 13CNMR peak is around 190ppm

2- use inadequate 13C-13C NMR spectroscopy to assign all carbons in your product.

3- according to my experiments, using mixed CDCl3-DMSO-d6 affects not only the chemical shift but also the number of peaks in CHNMR. the chemical shift was around 0.3 for my product. and in 13CNMR you will see 13CNMR for DMSO as well as CDCl3

i hope my answer would be useful for all researchers encountering the same problem.