Coinmama is a very legitimate and reputable platform, so regarding that, you shouldn't have any issue using them. If it makes you feel more relaxed, I have purchased several times using them before. However, I had to stop using them recently, due to the annoyingly delays in transactions and asides that I have also noticed a lot of users having problem with verification issues. I am not sure if this is a technical issue on their side, but I normally do not like gambling with my funds, if you know what I mean.
Final answer, in the short term, I may just use another exchange right now if I were you. At least, I am not having any issue with Coinbase for now. In the long term, if you wish, you can decide to revisit them, but do some research to see what users are saying first before going ahead.
Thank you very much... can you please recommend any other exchange other than Coinbase? where I can buy BTC using credit card?