Frequency can differ from area to area. Wireless carriers do not always control their preferred frequency in every market. Verizon and AT&T usually have their 4g LTE in the 700mhz area. 3g and 1x is usually handled around 800mhz and 1900mhz. This is for Send/receive. I said usually. There are many exceptions.
You mentioned repeater. What is your definition of repeater? Is it an actual cellphone booster? What type? Brand? Model? External antenna type?
Cell boosters need something to boost. There are areas with no cell service at all. No booster can help in these areas. Some areas AT&T and Tmobile work while other areas are friendly to Sprint and Verizon. What is the actual signal level on your phone while outside? I'm not asking how many bars of service. Bars that indicate cell signal are mostly useless. The bar level can vary from phone to phone for no reason. Need real signal level. Google can help you determine how to find signal level on your phone.
Some boosters are better than others. Need more information to assist. What carrier and phone? Do any neighbors have usable cell signal?